Set Theory Talks

Global set theory seminar and conference announcements

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 26, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 19, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Louise Dupuis (Paris Dauphine) and Matteo Michelini (Eindhoven).
Title: MySide bias in scientific debates

Abstract: Recent research in cognitive science supports the idea that scientific reasoning is influenced by myside resp. confirmation bias — a tendency to prioritize the search and generation of arguments that support one’s views, rather than arguments that would undermine it and, consequently, to apply more critical scrutiny to opposing than to one’s own stances (Mercier, 2017, Mercier, 2014). Even though myside bias may pull scientists away from the truth, its effects could be mitigated by certain socio-epistemic mechanisms. Moreover, if kept under control — so the argument goes — myside bias may have a positive impact on inquiry by generating an efficient division of cognitive labour. While this view stands in sharp contrast to the common take on confirmation bias as epistemically pernicious, it coheres with recent arguments from the philosophy of science that confirmation bias can be beneficial for group inquiry (Smart, 2018, Peters, 2020). This raises the question under which conditions (if any) myside bias plays such a positive role. In this paper we investigate this question by means of an argumentative agent-based model. Our results suggest that the myside bias may have an ambivalent effect on scientific debates. On the one hand, biased scientists tend to explore the given topic to a greater extent, which may facilitate a more thorough inquiry. On the other hand, they are also less likely to change their mind, which can be especially damaging in case they have reached a consensus on a wrong point of view.

Note: This is joint work with Dunja Šešelja, Juliette Rouchier, Gabriella Pigozzi, Annemarie Borg, and Christian Straßer.




- - - - Tuesday, Sep 27, 2022 - - - -



- - - - Wednesday, Sep 28, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York, Room 6417
Date and Time:     Wednesday September 28, 2022, 7:00 - 8:30 PM.
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     James Torre
Title:     Diagonalization, and the Limits of Limitative Theorems.


- - - - Thursday, Sep 29, 2022 - - - -



- - - - Friday, Sep 30, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, September 30, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Victoria Gitman, CUNY

Jensen's forcing at an inaccessible

Jensen constructed in , using , a subposet of the Sacks forcing with the ccc and the property that it adds a unique generic real over  (in contrast to, say, Cohen forcing which adds continuum many generic reals). He used what came to be known as Jensen's forcing to show that, consistently, there can be a -definable non-constructible real. The 'uniqueness of generic reals' property of Jensen's forcing extends to products of Jensen's forcing and to finite iterations, when forcing over . Indeed, a Jensen-like forcing with the same uniqueness properties can be constructed in any universe with a -sequence. In a joint work with Friedman and Kanovei, we used a tree iteration of Jensen's forcing to construct (in a symmetric submodel of the forcing extension) a model of full second-order arithmetic  with the choice scheme in which the dependent choice scheme failed for a -assertion (this is optimal because  with the choice scheme implies dependent choice for -assertions). In this talk, I will present a generalization of Jensen's forcing to forcing with perfect -trees for an inaccessible cardinal . I will show that Jensen's forcing at an inaccessible has the same 'uniqueness of generics' properties as Jensen's forcing. One of the goals of this work is to prove an analogue of the second-order arithmetic result for second-order set theory by showing that the dependent choice scheme is independent of the second-order Kelley-Morse set theory with the choice scheme. This is joint work with Sy-David Friedman.





Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday September 30, 2:00pm-3:30pm, Room 6417

Hans Schoutens, CUNY
The model-theory of categories

One could make the claim that category theory is as foundational as set-theory or model-theory. So, we should be able to transfer from one perspective to the other. In this talk, I will consider one aspect of this meta-equivalence, by introducing a theory in a very simple, one-sorted(!) language, whose models are all categories admitting a terminal object (many categories do). Many categorical constructions then turn out to be first-order. But something even more strange happens: standard categories (like the category of Abelian groups) become actually universal models! I'll explain this apparent contradiction.

In the second part of the talk, I will concentrate on one particularly interesting category: that of compact Hausdorff spaces. I will show that we can recover the natural numbers  and the reals , or rather, (the isomorphism classes of) their compactifications  and , by parameter-free definitions, including their order relation, addition and multiplication. Moreover, in any category that is elementary equivalent to the category of compact Hausdorff spaces, the resulting objects are then a model of PA and a real closed field respectively. Full disclosure: while I have a complete proof for the first assertion, the second is still conjectural.

Apart from some basic model-theory, category theory and topology, everything else will be explained in the talk and so it should be accessible to many.




Next Week in Logic at CUNY:

- - - - Monday, Oct 3, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 19, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Yale Weiss (CUNY)
Title: The best of all possible Leibnizian completeness theorems

Abstract: Leibniz developed several arithmetical interpretations of the assertoric syllogistic in a series of papers from April 1679. In this talk, I present his most mature arithmetical semantics. I show that the assertoric syllogistic can be characterized exactly not only in the full divisibility lattice, as Leibniz implicitly suggests, but in a certain four-element sublattice thereof. This refinement is also shown to be optimal in the sense that the assertoric syllogistic is not complete with respect to any smaller sublattice using Leibniz’s truth conditions.



- - - - Tuesday, Oct 4, 2022 - - - -



- - - - Wednesday, Oct 5, 2022 - - - -



- - - - Thursday, Oct 6, 2022 - - - -



- - - - Friday, Oct 7, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, October 7, 11am NY time
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Sakae Fuchino, Kobe University
TBA




Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday October 7, 2:00pm-3:30pm, Room 6417
Krzysztof Krupiński University of Wroclaw


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

MLTCS logic seminar

Prague Set Theory Seminar
Dear all, There will be a joint seminar of the MLTCS department on this Monday, September 26th, at 16:00. This time we will have a set theory talk, everybody is welcome to join. See the forwarded announcement below. (Apologies for possibly multiple copies.) Best, David **************************************************************************** [Logic-seminar] seminar Monday at 16:00, coffee at 15:45 Dear Colleagues, in our department we decided to have a Joint Seminar at least once per semester. The idea is to learn what different groups in our department are working on. Therefore the lectures on these meetings are intended for a larger logic community. For those who do not come regularly to our logic seminar, this is an opportunity to listen to a talk that you may understand without a special background in the topic. Location: Institute of Mathematics CAS, Zitna 25, blue lecture hall, rear building, ground floor Monday September 26, 15:45 coffee, 16:00 seminar start Speaker: Chris Lambie-Hanson, IM CAS Title: Compactness and incompactness in set theory, with applications to uncountable graphs The study of compactness phenomena at uncountable cardinals has been a central line of research in combinatorial set theory since the mid-twentieth century. In the first part of this talk, we will give a broad overview of this area of research and survey some of its most prominent results. We will then look at a few recent results concerning compactness phenomena for uncountable graphs. We first look at possible generalizations of the de Bruijn-Erdos compactness theorem for chromatic numbers to uncountable cardinalities, in particular showing that consistently there are large uncountable graphs witnessing extreme failures of compactness for, e.g., the property of having a countable chromatic number. We then turn to the study of the structure of the collections of finite subgraphs of uncountably chromatic graphs, answering a question of Erdos, Hajnal, and Szemeredi about the growth rates of chromatic numbers in such collections of finite subgraphs. Pavel Pudlak _______________________________________________ Logic-seminar mailing list Logic-seminar@math.cas.cz https://list.math.cas.cz/listinfo/logic-seminar

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 19, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 19, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Bokai Yao (Notre Dame), 
Reflective Mereology

Abstract: I explore a new theory of mereology based on a mereological reflection principle. Reflective mereology has natural fusion principles but also refutes certain principles of classical mereology such as Universal Fusion and Fusion Uniqueness. Moreover, reflective mereology avoids Uzquiano’s cardinality problem–the problem that classical mereology tends to clash with set theory when they both quantify over everything. In particular, assuming large cardinals, I construct a natural model of reflective mereology and second-order ZFCU with Limitation of Size. In the model, classical mereology holds when the quantifiers are restricted to the urelements.



- - - - Tuesday, Sep 20, 2022 - - - -

Computational Logic Seminar
Fall Semester 2022
Tuesday, September 20
Time 2:00 - 4:00 PM
Room 3310-B
Speaker: Vincent Alexis Peluce, Graduate Center
Title:   Classical Reasoning in the Justification Paradigm

Abstract:  Artemov, building upon a tradition beginning with Kolmogorov and Gödel, developed a paradigm for understanding constructive reasoning in terms of classical proofs. Kolmogorov-Gödel-Artemov constructivism flies in the face of the usual understanding of constructive reasoning as being distinguished from classical reasoning in terms of its theory of truth. Is there something that stands to traditional classical reasoning as Kolmogorov-Gödel-Artemov constructivism stands to constructive reasoning? In this paper we develop an affirmative answer to this question by presenting a justification account of classical reasoning in terms of explicit justification. The traditional truth paradigm account of classical reasoning leads to the well-known paradoxes of material implication. We show that the justification account of classical reasoning avoids this problem.



- - - - Wednesday, Sep 21, 2022 - - - -



- - - - Thursday, Sep 22, 2022 - - - -



- - - - Friday, Sep 23, 2022 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday September 23, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Interpreting a field in its Heisenberg group

The Heisenberg group G(F) of a field F is the group of upper triangular matrices in GL_3(F), with 1's along the diagonal and 0's below it. This group is obviously interpretable (indeed definable) in the field F. Mal'cev showed that one can recover F from G(F), and indeed that there is an interpretation of F in G(F) using two parameters. Any two noncommuting elements of G(F) can serve as the parameters, but Mal'cev was unable to produce an interpretation without parameters.

After introducing the notions of a computable functor and an effective interpretation, we will present joint work showing that there is an effective interpretation of each countable field in its Heisenberg group, without parameters, uniformly in F. (That is, the same formulas give the interpretation, no matter which field F we consider.) Moreover, from the effective interpretation we will then extract a traditional interpretation without parameters, in the usual model-theoretic sense. Finally we will note that, whereas Mal'cev's result actually gives a definition of F in G(F), there is no parameter-free definition of F there.

This work is joint with Rachael Alvir, Wesley Calvert, Grant Goodman, Valentina Harizanov, Julia Knight, Andrey Morozov, Alexandra Soskova, and Rose Weisshaar.




Next Week in Logic at CUNY:

- - - - Monday, Sep 26, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 19, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Louise Dupuis (Paris Dauphine) and Matteo Michelini (Eindhoven).
Title: MySide bias in scientific debates

Abstract: Recent research in cognitive science supports the idea that scientific reasoning is influenced by myside resp. confirmation bias — a tendency to prioritize the search and generation of arguments that support one’s views, rather than arguments that would undermine it and, consequently, to apply more critical scrutiny to opposing than to one’s own stances (Mercier, 2017, Mercier, 2014). Even though myside bias may pull scientists away from the truth, its effects could be mitigated by certain socio-epistemic mechanisms. Moreover, if kept under control — so the argument goes — myside bias may have a positive impact on inquiry by generating an efficient division of cognitive labour. While this view stands in sharp contrast to the common take on confirmation bias as epistemically pernicious, it coheres with recent arguments from the philosophy of science that confirmation bias can be beneficial for group inquiry (Smart, 2018, Peters, 2020). This raises the question under which conditions (if any) myside bias plays such a positive role. In this paper we investigate this question by means of an argumentative agent-based model. Our results suggest that the myside bias may have an ambivalent effect on scientific debates. On the one hand, biased scientists tend to explore the given topic to a greater extent, which may facilitate a more thorough inquiry. On the other hand, they are also less likely to change their mind, which can be especially damaging in case they have reached a consensus on a wrong point of view.

Note: This is joint work with Dunja Šešelja, Juliette Rouchier, Gabriella Pigozzi, Annemarie Borg, and Christian Straßer.




- - - - Tuesday, Sep 27, 2022 - - - -



- - - - Wednesday, Sep 28, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York, Room 6417
Date and Time:     Wednesday September 28, 2022, 7:00 - 8:30 PM.
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     James Torre
Title:     Diagonalization, and the Limits of Limitative Theorems.


- - - - Thursday, Sep 29, 2022 - - - -



- - - - Friday, Sep 30, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, September 30, 12:15pm NY time
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Victoria Gitman, CUNY

Jensen's forcing at an inaccessible

Jensen constructed in , using , a subposet of the Sacks forcing with the ccc and the property that it adds a unique generic real over  (in contrast to, say, Cohen forcing which adds continuum many generic reals). He used what came to be known as Jensen's forcing to show that, consistently, there can be a -definable non-constructible real. The 'uniqueness of generic reals' property of Jensen's forcing extends to products of Jensen's forcing and to finite iterations, when forcing over . Indeed, a Jensen-like forcing with the same uniqueness properties can be constructed in any universe with a -sequence. In a joint work with Friedman and Kanovei, we used a tree iteration of Jensen's forcing to construct (in a symmetric submodel of the forcing extension) a model of full second-order arithmetic  with the choice scheme in which the dependent choice scheme failed for a -assertion (this is optimal because  with the choice scheme implies dependent choice for -assertions). In this talk, I will present a generalization of Jensen's forcing to forcing with perfect -trees for an inaccessible cardinal . I will show that Jensen's forcing at an inaccessible has the same 'uniqueness of generics' properties as Jensen's forcing. One of the goals of this work is to prove an analogue of the second-order arithmetic result for second-order set theory by showing that the dependent choice scheme is independent of the second-order Kelley-Morse set theory with the choice scheme. This is joint work with Sy-David Friedman.





Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday September 30, 2:00pm-3:30pm, Room 6417

Hans Schoutens, CUNY
The model-theory of categories

One could make the claim that category theory is as foundational as set-theory or model-theory. So, we should be able to transfer from one perspective to the other. In this talk, I will consider one aspect of this meta-equivalence, by introducing a theory in a very simple, one-sorted(!) language, whose models are all categories admitting a terminal object (many categories do). Many categorical constructions then turn out to be first-order. But something even more strange happens: standard categories (like the category of Abelian groups) become actually universal models! I'll explain this apparent contradiction.

In the second part of the talk, I will concentrate on one particularly interesting category: that of compact Hausdorff spaces. I will show that we can recover the natural numbers  and the reals , or rather, (the isomorphism classes of) their compactifications  and , by parameter-free definitions, including their order relation, addition and multiplication. Moreover, in any category that is elementary equivalent to the category of compact Hausdorff spaces, the resulting objects are then a model of PA and a real closed field respectively. Full disclosure: while I have a complete proof for the first assertion, the second is still conjectural.

Apart from some basic model-theory, category theory and topology, everything else will be explained in the talk and so it should be accessible to many.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, There will be no Wednesday seminars during the upcoming three weeks. (Many people will be absent on Sept. 21, state holiday on Sept. 28, Institute's off-site meeting on Oct. 5.) The seminar should meet next time on Wednesday October 12 for a talk of Borisa Kuzeljevic. Best, David

Logic Seminar 14 September 2022 17:00 hrs at NUS by Ammar Fathin Sabili

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 14 September 2022, 17:00 hrs Place: NUS, Department of Mathematics, S17#04-05 Speaker: Ammar Fathin Sabili Title: Alternating automatic register machines URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: We introduce and study a new computation model called an Alternating Automatic Register Machine (AARM). An AARM possesses a basic features of a conventional register machine and an alternating Turing machine, but can carry out computations using bounded automatic relations in a single step. One particular finding is that an AARM can recognize some NP-complete problems, including CNF-SAT (using a particular encoding), in logstar n + O(1) steps. Furthermore, we also show that padding the input with a polynomial-size string allows to recognise exactly the sets in the polynomial hierarchy using logstar n + O(1) steps. This is joint work with Gao Ziyuan, Sanjay Jain, Li Zeyong and Frank Stephan. A technical report is on https://arxiv.org/abs/2111.04254 an the paper is accepted for the International Colloquium on Theoretical Aspects of Computing (ICTAC 2022).

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 12, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 12, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Speaker: Yasuo Deguchi, Kyoto University
Title: Logic of Presence

Abstract: This talk will propose a new modality within the framework of possible worlds, i.e., presence or present world. Presence is defined in terms of mutual or two-ways intentionality: An object X is present to an intentional agent A in the actual world iff A has active and passive intentionalities toward X, where active intentionality means that A has intentionality to X (e.g., A loves X), and passive intentionality means that A has self-awareness/consciousness as being an object of X’s intentionality (e.g., X loves A). Some actual agents such as your partner is actual and present entity for you, while other actual objects such as minute physical events in an unknown faraway galaxy are actual but not present entities for you. Some counterfactual agents such as those in a digital virtual reality can be counterfactual but present agents for you, while some other counterfactual entities are simply counterfactual and non-present for you. This talk claims that this present approach to virtual reality is better than Chalmers’ virtual realism and Ryan’s recentering approach. This talk also outlines the logic of presence that is an extension of Priest-Berto’s logic of intentionality, being based on possible worlds semantics.




- - - - Tuesday, Sep 13, 2022 - - - -



- - - - Wednesday, Sep 14, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York, Room 6417
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Prakash Panangaden, McGill University.
Date and Time:     Wednesday September 14, 2022, 7:00 - 8:30 PM.
Title:     Quantitative Equational Logic.
 

- - - - Thursday, Sep 15, 2022 - - - -



- - - - Friday, Sep 16, 2022 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday September 16, 2:00pm-3:30pm, Room 6417

Gunter Fuchs, CUNY
The blurry HOD hierarchy

Classically, an object is ordinal definable if it is the unique one satisfying a formula with ordinal parameters. Generalizing this concept, given a cardinal , I call an object -blurrily ordinal definable if it belongs to an ordinal definable set with fewer than  elements (called a -blurry definition). By considering the hereditary versions of this notion, one arrives at a hierarchy of inner models, indexed by cardinals : the collection of all hereditarily -blurrily ordinal definable sets, which I call -HOD. In a ZFC-model, this hierarchy spans the entire spectrum from HOD to V.

The special cases  and  have been previously considered, but no systematic study of the general setting has been carried out, it seems. One main aspect of the analysis is the notion of a leap, that is, a cardinal at which a new object becomes hereditarily blurrily definable.

In this talk, I will focus on the ZFC-provable structural properties of the blurry HOD hierarchy, which turn out to be surprisingly plentiful. So for the most part, the talk will be forcing-free. Time permitting, I may hint at the result of the equiconsistency between the least leap being the successor of a singular strong limit cardinal and the existence of a measurable cardinal, for which, admittedly, forcing is used in one direction.





Next Week in Logic at CUNY:

- - - - Monday, Sep 19, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, Sept 19, 4.15-6.15 (NY time), GC 7315
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Bokai Yao (Notre Dame), 
Reflective Mereology

Abstract: I explore a new theory of mereology based on a mereological reflection principle. Reflective mereology has natural fusion principles but also refutes certain principles of classical mereology such as Universal Fusion and Fusion Uniqueness. Moreover, reflective mereology avoids Uzquiano’s cardinality problem–the problem that classical mereology tends to clash with set theory when they both quantify over everything. In particular, assuming large cardinals, I construct a natural model of reflective mereology and second-order ZFCU with Limitation of Size. In the model, classical mereology holds when the quantifiers are restricted to the urelements.



- - - - Tuesday, Sep 20, 2022 - - - -



- - - - Wednesday, Sep 21, 2022 - - - -



- - - - Thursday, Sep 22, 2022 - - - -



- - - - Friday, Sep 23, 2022 - - - -

Logic Workshop
CUNY Graduate Center
Hybrid (email Victoria Gitman for meeting id)
Friday September 23, 2:00pm-3:30pm, Room 6417

Russell Miller, CUNY
Interpreting a field in its Heisenberg group

The Heisenberg group G(F) of a field F is the group of upper triangular matrices in GL_3(F), with 1's along the diagonal and 0's below it. This group is obviously interpretable (indeed definable) in the field F. Mal'cev showed that one can recover F from G(F), and indeed that there is an interpretation of F in G(F) using two parameters. Any two noncommuting elements of G(F) can serve as the parameters, but Mal'cev was unable to produce an interpretation without parameters.

After introducing the notions of a computable functor and an effective interpretation, we will present joint work showing that there is an effective interpretation of each countable field in its Heisenberg group, without parameters, uniformly in F. (That is, the same formulas give the interpretation, no matter which field F we consider.) Moreover, from the effective interpretation we will then extract a traditional interpretation without parameters, in the usual model-theoretic sense. Finally we will note that, whereas Mal'cev's result actually gives a definition of F in G(F), there is no parameter-free definition of F there.

This work is joint with Rachael Alvir, Wesley Calvert, Grant Goodman, Valentina Harizanov, Julia Knight, Andrey Morozov, Alexandra Soskova, and Rose Weisshaar.


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

CMU Math Logic Seminar : First three lectures of the semester

Carnegie Mellon Logic Seminar
TUESDAY, September 13, 2022 Mathematical Logic Seminar: 3:30 - 4:30 P.M. Eastern, Online, Rick Statman, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Cayley Monoids ABSTRACT: Everyone is familiar with Cayley's regular representation of groups in the symmetric group. And, if you think about monoids at all, you noted that it applies in a limited way to monoids. The notion of a Cayley monoid is just an internalization of this type of representation. There are many examples of Cayley monoids. Some of these are obtained from the group of a monoid acting on the monoid itself. There are some interesting special cases of Cayley monoids with strong <_{L} commutativity properties. An example is provided by the monoid Z*Q where Q is the quaternion group. In these cases we say that the Cayley monoid has an autonomous commutator. Here we will show that every monoid can be extended to a Cayley monoid with an autonomous commutator. TUESDAY, September 20, 2022 Mathematical Logic Seminar: 3:30 - 4:30 P.M. Eastern, Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Extender based forcing and cardinal invariants of singular cardinals ABSTRACT: (Joint work with Charles Morgan) Many of the cardinal invariants of the continuum (EG the bounding number) generalise in a reasonable way to uncountable regular cardinals, but not to singular cardinals. I will discuss a cardinal invariant (the ultrafilter character spectrum) which does generalise, and how to control its value by forcing. TUESDAY, September 27, 2022 Mathematical Logic Seminar: 3:30 - 4:30 P.M. Eastern, Online, Riley Thornton, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Complexity and dichotomy theorems ABSTRACT: I will survey some recent results on projective complexity, and I will explain what they tell us about dichotomy theorems in descriptive set theory. In particular, I will explain how the (unfortunately named) CSP Dichotomy Theorem implies a formal connection between computational and projective complexity and how this tells us exactly which graph homomorphism problems admit descriptive set theoretic dichotomies.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 14th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Indestructible reaping families (continued) I will prove that complements of various well-known ideals are reaping families indestructible with Sacks forcing. This is a continuation of a talk from Wednesday September 7th. The talk will start with brief overview of the background from the previous talk necessary to follow the proofs. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Sep 5, 2022 - - - -



- - - - Tuesday, Sep 6, 2022 - - - -



- - - - Wednesday, Sep 07, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York, Room 6417
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html 
Speaker:     Sergei Burkin, University of Tokyo.
Date and Time:     Wednesday September 7, 2022, 7:00 - 8:30 PM.
Title:     Segal conditions and twisted arrow categories of operads.

Abstract: Several categories, including the simplex category Delta and Moerdijk-Weiss dendroidal category Omega, allow to encode structures (in this case categories and operads respectively) as Segal presheaves. There are other examples of such categories, which were defined intuitively, by analogy with Delta. We will describe a general construction of categories from operads that produces categories that admit Segal presheaves. This construction explains why these categories appear in homotopy theory, why these allow to encode homotopy coherent structures as simplicial presheaves that satisfy weak Segal condition. Further generalization of this construction to clones shows that these categories are not as canonical as one might have hoped.





- - - - Thursday, Sep 08, 2022 - - - -



- - - - Friday, Sep 09, 2022 - - - -

Model Theory Seminar
September 9, 12:15pm NY time, GC Room 6495
Hybrid (email Victoria Gitman for meeting id)
Two longstanding open problems in positive characteristic and their relation to valuation theory
Franz-Viktor Kuhlmann, University of Szczecin

Abstract: Since Hironaka proved resolution of singularities over base fields of characteristic zero in 1964, the corresponding problem in positive characteristic has remained open, and so has its local form, called local uniformization. The latter is in fact a valuation theoretical problem, due to ideas of Zariski. I will present these ideas and show the connection of local uniformization with the structure theory of valued function fields. The positive characteristic case is so much harder than the characteristic zero case because of the phenomenon of the defect. I will define it and sketch strategies to either avoid it or work around it; these led to some partial solutions to the local uniformization problem.

In 1965, one year after Hironaka, Ax and Kochen used the model theory of valued fields to prove a corrected version of Artin's Conjecture. Thereafter they, and independently Ershov, proved the decidability of the elementary theory of the fields of p-adic numbers. The problem for their counterpart in positive characteristic, the Laurent series fields over finite fields, is still open. I will explain which tools can be used to prove decidability. Via general principles of model theory, the task can be reduced to proving embedding lemmas for valued function fields, which I will describe. This in turn requires a good structure theory for such valued function fields, and this is what our decidability problem has in common with the local uniformization problem. In analogy to the local uniformization problem, our theory of the defect has led to partial solutions, in the sense of new model theoretic results about certain classes of valued fields in positive characteristic.



Next Week in Logic at CUNY:

- - - - Monday, Sep 12, 2022 - - - -



- - - - Tuesday, Sep 13, 2022 - - - -



- - - - Wednesday, Sep 14, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York, Room 6417
URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Speaker:     Prakash Panangaden, McGill University.
Date and Time:     Wednesday September 14, 2022, 7:00 - 8:30 PM.
Title:     Quantitative Equational Logic.
 

- - - - Thursday, Sep 15, 2022 - - - -



- - - - Friday, Sep 16, 2022 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Logic Seminar Wed 7 Sept 2022 17:00 hrs at NUS S17#04-05 by Liao Yuke

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 07 September 2022, 17:00 hrs Location: National University of Singapore, Department of Mathematics, Block S17, Seminar Room #04-05 Speaker: Liao Luke Title: A computable coloring without Pi^0_3 witness with apartness for Hindman theorem Abstract: We construct a computable coloring function such that any Pi^0_3 set with apartness can not be a witness of Hindman theorem for this coloring. And we can modify the coloring function and drop the condition "with apartness". URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday September 7th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Indestructible reaping families (continued) I will prove that complements of various well-known ideals are reaping families indestructible with Sacks forcing. This is a continuation of a talk I gave in June, however, the talk will be accessible without the prior knowledge of the topics covered in the previous talk. Best, David

Logic Seminar 31 Aug 2022 at 17:00 hrs at NUS by Yang Yue

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 31 August 2022, 17:00 hrs Place: NUS, Department of Mathematics, Room S17#04-05 Speaker: Yang Yue Title: The Strong Minimal Pair Problem Abstract: A pair (a,b) of nonzero r.e. Turing degrees is called a strong minimal pair iff the recursive Turing degree is the only common lower bound and if every nonzero Turing degree bounded by a has with b a join greater or equal a. We show that such strong minimal pairs do not exist. Joint work with Cai Mingzhong, Liu Yiqun, Liu Yong and Peng Cheng URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Logic Seminar at NUS on Wed 24/08/2022 17:00 hrs by Goh Jun Le

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 24 August 2022, 17:00 hrs Location: Department of Mathematics, NUS, Room S17#04-05 Speaker: Goh Jun Le Title: An exact pair in the Sigma^0_2 enumeration degrees URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: We present ongoing work with Steffen Lempp, Ng Keng Meng and Mariya Soskova on the algebraic structure of the Sigma^0_2 e-degrees, i.e., the quotient structure on the Sigma^0_2 subsets of the natural numbers induced by enumeration reducibility. The Sigma^0_2 e-degrees are analogous to the r.e. Turing degrees in some ways, but an elementary difference between them was exhibited by Ahmad (1998): In the former structure there are incomparable degrees a and b such that if x < a, then x < b. (Such a and b cannot exist in the r.e. Turing degrees by the Sacks splitting theorem.) Ahmad also showed that this phenomenon cannot occur symmetrically, i.e., there cannot be incomparable degrees a and b such that x < a if and only if x < b. In contrast, we show that there are incomparable degrees a, b and c such that x < a if and only if (x < b and x < c). In other words, the ideal {x: x < a} admits an exact pair (b,c). This result constitutes progress towards our ultimate goal of algorithmically deciding the truth of all two-quantifier sentences in the Sigma^0_2 e-degrees.

Logic Seminar 17 Aug 2022 17:00 hrs at NUS by Wong Tin Lok

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 17 August 2022, 17:00 hrs Location: S17#04-05, Department of Mathematics, NUS Speaker: Wong Tin Lok Title: Another quantifier-elimination result in arithmetic under negated induction URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: I will present another quantifier-elimination result in arithmetic under negated induction. This gives new information about pigeonhole principles and expansions to second-order models. Joint work with: David Belanger, CT Chong, Wei Li and Yue Yang

Logic Seminar Wednesday 10 Aug 2022 17:00 hrs at NUS, Room S17#04-05

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 10 August 2022, 17:00 hrs Talk in person: Department of Mathematics, Room S17#04-05 Speaker: Tran Chieu-Minh Title: O-minimal Methods and Generalized Sum-Product Phenomena For a bivariate P(x,y) in R[x,y] - (R[x] union R[y]), we show that for all finite subsets A of R, |P(A,A)| is greater or equal alpha |A|^(5/4) with alpha = alpha(deg P) being a real number greater than 0, P(x,y)=f(gamma u(x)+delta u(y)) or P(x,y)=f(u^m(x)u^n(y)) for some univariate f, u R[t] - , constants gamma, delta in R - {0} and m, n in {1,2,3,...}. This resolves the symmetric nonexpanders classification problem proposed by de Zeeuw and is a step towards the analog for polynomials of the Erdoes-Szemeredi sumproduct Conjecture. The proofs of our results use tools from semialgebraic / o-minimal geometry. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday August 10th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Michael Hrusak -- TBD updates at https://calendar.math.cas.cz/seminar-on-reckoning-actual The seminar should start meeting regularly again in September. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Omer Ben-Neria 
TITLE: Diamond, Compactness, and product approximations

ABSTRACT: It is well known that certain compactness principles imply the existence of diamonds. A long-standing open problem in the area asks if a weakly compact cardinal must carry a diamond sequence.  We introduce a weak form of the diamond principle given in terms of function estimates on products of cardinals. We use the weaker principle to find new methods for forcing the failure of diamonds at inaccessible, Mahlo, and stationary reflecting cardinals and show that the weaker principle must hold at a weakly compact cardinal. This is joint work with Jing Zhang.

DATE: Wednesday, 20 July 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place in person at IMUB, and online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



RIMS Set Theory Workshop: October 25-28, 2022

Conference
Let me announce RIMS Set Theory Workshop 2022. This year’s workshop will be a hybrid one at RIMS, Kyoto University, Japan and online via Zoom. RIMS Set Theory Workshop 2022 - New Developments in Forcing and Cardinal Arithemtic - dates: October 25th — 28th, 2022 venue: RIMS, Kyoto University, Japan & Online via Zoom organizer: Hiroshi Sakai (Kobe) web page: https://sites.google.com/view/rimssettheory2022/home We plan the following mini-course and invited talks: Mini-Course: - Itay Neeman (UCLA) Invited Talks: - David Aspero (East Anglia) - Teruyuki Yorioka (Shizuoka) - Rahman Mohammadpour (TU Vienna) We also encourage you to contribute with talks. Of course, we welcome participations without talks. Abstract submission and registration can be done at the web page of the workshop. Dead lines are as follows: Abstract Submission: until September 10th Registration: until October 15th Please feel free to contact the organizer (hrshsakai@gmail.com) if you have any questions. We are looking forward to your participation!
Link to more info

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 29th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The seminar will not meet during July. The seminar might meet next time on Wednesday August 10th for a talk of Michael Hrusak. Regular seminars should start again in September. Program (June 29): Michal Doucha -- Generic actions of groups on the Cantor space (continued) In the second part of the talk I will continue with an introduction to the symbolic dynamics. I will introduce notions such as shifts of finite type, sofic shifts, and I will mention the Curtis-Hedlund-Lyndon theorem which describes continuous equivariant maps between shifts. Then with this knowledge, I will show how certain inverse limits of shifts of finite type (or of sofic shifts) define generic actions on the Cantor space. I won't expect the audience to remember too much from the first talk. Best, David

(KGRC) seminar talks Tuesday, June 28 and Thursday, June 30

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until August 31. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30, see below. Severin Mejak (hosts: Vera Fischer, David Schrittesser) visits the KGRC from July 5 to July 14. Justin Moore (host: Vera Fischer) visits the KGRC from July 15 to July 23. Jeffrey Bergfalk (host: Vera Fischer) visits the KGRC from July 16 to July 23. Leandro Aurichi (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to August 6. Frank Tall (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. Peter Nyikos (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, June 28 Doctoral and master students specialising in set theory will speak on selected topics from their work during the semester. Detailed program with titles and abstracts is in the attachment. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 3:00pm - 4:30pm (Fortunato, Lukas and Alexander): 1st floor Seminar room 10 4:45pm - 6:15pm (Ömer, Julia and Roman): 2nd floor Seminar room 17 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talks, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 30 "Set theory and coronas of C*-algebras" Alessandro Vignati (Université de Paris, FR) As abelian C*-algebras correspond functorially to locally compact Hausdorff space, studying C*-algebras is often viewed as noncommutative topology. A locally compact Hausdorff space X can be embedded densely in its Čech-Stone compactification beta X, the `largest compact space in which X sits densely'. Similarly, to every nonunital C*-algebras A one can associate `the largest unital C*-algebra in which A sit densely', the multiplier algebra M(A). Corona C*-algebras, quotients of the form M(A)/A, correspond to Čech-Stone remainders (space of the form beta X minus X). Čech-Stone remainders have been studied with set theoretical methods since the '80s. The work of Rudin, Shelah, Steprans, Velickovic, and Farah among others, showed that the structure of the space beta X minus X, and its autohomeomorphisms, often depend on the set theoretic axioms in play. Similar phenomenons appear when studying corona C*-algebras, as Farah's work on the Calkin algebra (the corona algebra of the compact operators) witnesses. This talk is dedicated to overview how different axioms in set theory impact the structure of automorphisms of corona C*-algebras. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!
View attachment

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Jeffrey Bergfalk 
TITLE: Higher derived limits and higher dimensional partitions of partial orders
DATE: 22 June 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Set Theory Seminar Tuesday, June 21

Kurt Godel Research Center
David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21, see below. Gunter Fuchs (host: Vera Fischer) visits the KGRC from June 12 to June 18. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for this talk will be announced later. Justin Moore (host: Vera Fischer) visits the KGRC from July 15 to July 23. Leandro Aurichi (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to August 6. Frank Tall (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. Peter Nyikos (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, June 21 "The Ramsey property, MAD families, and their higher dimensional relatives" David Schrittesser (University of Toronto, Canada) Infinite maximal almost disjoint families, dubbed "MAD families" by A.R.D. Mathias, have long been an object of interest in set theory, topology, and other areas. A question which has been tossed around for quite a while was whether there can exist an analytic Fin^2-MAD family - that is, a two-dimensional variant of the usual notion of MAD family. Analytic (one-dimensional) MAD families cannot exist, so the conjecture has always been "no" - and indeed the answer is "no", as was shown in joint work with Törnquist and Bakke Haga in 2016. In 1969, Mathias asked whether Ramsey regularity rules out the existence of (one dimensional) MAD families. This question was answered positively in joint work with Törnquist in 2019. But now that we know that Fin^2 MAD families behave like MAD families in some respects, and that Ramsey regularity rules out (one dimensional) MAD families, does Ramsey regularity also rule out the two dimensional variant? Yes, Ramsey regularity rules out the existence of Fin^2 MAD families (also joint work with Asger Törnquist). The result even holds for J-MAD families, where J is an ideal in the smallest class containing the ideal of finite sets and closed under Fubini products. I will also report on work in progress with our student Severin Mejak. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Michal Doucha -- Generic actions of groups on the Cantor space In 2004, Kechris and Rosendal proved that there is a generic homeomorphism of the Cantor space. In other words, there is a generic action of the group of the integers on the Cantor space. Few years later, this was proved to be false when Z is replaced by Z^d, d>1, by Hochman, resp. to be still valid when Z is replaced by a general finitely generated free group, by Kwiatkowska. I found a characterization of countable groups admitting generic actions in terms of subshifts of finite type over such groups that allows to produce more examples and non-examples. I plan a gentle talk where I will not bother the audience with general groups (unless I am asked to do so) and just try to explain some ideas on the example of the integers. In particular, I will give an introduction to symbolic dynamics and shifts of finite type and say how with these objects we can construct the generic homeomorphism of the Cantor space. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. The program is not yet decided, walk-in speakers will be welcome. Best, David

Krzysztof Zakrzewski, Elementary submodels and Corson-compact spaces

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 14.06.2022, at 13.15, room 403 Speaker: Krzysztof Zakrzewski (MIM UW) Title: Elementary submodels and Corson-compact spaces. Abstact: "We will present a characterisation of Corson-compact spaces using elementary submodels and use it to show a theorem proved earlier by Gul'ko stating that a Hausdorff continuous image of a Corson-compact space is Corson-compact." This seems to be the last talk of this semester. https://www.impan.pl/~set_theory/Seminar/

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Kameryn William 
TITLE: Inner mantles: the good, bad, and ugly
DATE: 15 June 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Cross-Alps Logic Seminar (speaker: Sonia L'Innocente)

Cross-Alps Logic Seminar
On Friday 10.06.2022 at 16:00
Sonia L'Innocente (University of Camerino)
will give a talk on
A factorisation theory for generalised power series

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


Mail priva di virus. www.avast.com

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All,
on Wednesday, the seminar will take place in hybrid from at the IMUB.
Hope to see you there!
Best,
Joan

Inici del missatge reenviat:

De: Joan Bagaria <joan.bagaria@icrea.cat>
Tema: Barcelona Set Theory Seminar
Data: 3 de juny de 2022, 8:56:35 CEST

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   William Mance
TITLE: Descriptive complexity in number theory and dynamics
DATE: 8 June 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.


Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   William Mance
TITLE: Descriptive complexity in number theory and dynamics
DATE: 8 June 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.


Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, There will be no seminar next week, Wednesday June 8th (many regular seminar participants are away). It is unclear whether the seminar will regularly meet in June and during the summer. No announcement = no seminar. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

This will be our final mailing of "This Week in Logic" for the Spring 2022 semester.  We will resume regular mailings at the end of August (but will also send out special announcements for any summer talks).

May your time between semesters be fruitful,
Jonas


This Week in Logic at CUNY:

- - - - Monday, May 30, 2022 - - - -



- - - - Tuesday, May 31, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 31, 8pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Tin Lok Wong, National University of Singapore

Another quantifier-elimination result in arithmetic under negated induction

In a paper published in 1990, Kossak showed that all countable models of  collection where  induction fails have continuum-many automorphisms. We extract from his proof a(nother) quantifier-elimination result. This gives new information about pigeonhole principles and expansions to second-order models. The work is joint with David Belanger, CT Chong, Wei Li, and Yue Yang at the National University of Singapore.




- - - - Wednesday, Jun 1, 2022 - - - -



- - - - Thursday, Jun 2, 2022 - - - -



- - - - Friday, Jun 3, 2022 - - - -




Next Week in Logic at CUNY:

- - - - Monday, Jun 6, 2022 - - - -



- - - - Tuesday, Jun 7, 2022 - - - -



- - - - Wednesday, Jun 8, 2022 - - - -



- - - - Thursday, Jun 9, 2022 - - - -



- - - - Friday, Jun 10, 2022 - - - -



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
I would like to draw attention to the conference
“Functor Categories, Model Theory, and Constructive Category Theory”,
to be held July 11-15, 2022 at the University of Almería, Spain.
For more information visit
https://web.northeastern.edu/martsinkovsky/p/Conferences/Almeria2022/FM.html




- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Jakub Andruszkiewicz, Countable support iterations of proper forcing notions

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 31.05.2022, at 13.15, room 403 Speaker: Jakub Andruszkiewicz (UW/IM PAN) Title: Countable support iterations of proper forcing notions. Abstact: "We present a classical result concerning iterations of proper forcings, namely that the properness is preserved by countable support iterations. We will follow section 3 of "Tools for your forcing construction" by M. Goldstern." This seems to be the last talk of this semester.

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   William Chan
TITLE: Almost Disjoint Families under Determinacy
DATE: 1 June 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.





Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday June 1st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindřich Zapletal -- Noetherian graphs I define the class of Noetherian graphs. These are the graphs in which the canonical graph topology is Noetherian; there is also an equivalent combinatorial definition. I show that closed Noetherian graphs without infinite cliques have countable chromatic number and are easier to color than most. There are many examples. Best, David

Cross-Alps Logic Seminar (speaker: Takako Nemoto)

Cross-Alps Logic Seminar
On Friday 27.05.2022 at 16:00
Takako Nemoto (Japan Advanced Institute of Science and Technology)
will give a talk on
Determinacy of infinite games and reverse mathematics

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.



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(KGRC) (update: Zoom) Logic Colloquium talk Thursday, June 2

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for this talk will be announced later. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. James Mitchell (host: Vera Fischer) visits the KGRC until May 28. Yann Peresse (host: Serhii Bardyla) visits the KGRC until May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC until May 28. Gunter Fuchs (host: Vera Fischer) visits the KGRC from June 12 to June 18 and gives a talk on June 14. Details for this talk will be announced later. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for this talk will be announced later. Leandro Aurichi (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to August 6. Peter Nyikos (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. Frank Tall (host: Lyubomyr Zdomskyy) visits the KGRC from July 18 to July 22. * * * Please note that there will be no talk in the Set Theory Research Seminar on Tuesday, May 31. * * * Logic Colloquium Kurt Gödel Research Center Thursday, June 2 "The metamathematics of $\Pi^1_2$ sentences" Juan Aguilera (TU Wien) We will survey some recent results on the metamathematics of $\Pi^1_2$ sentences. Most of the work involves a kind of Proof Theory analogous to classical ordinal analysis, but focused on a $\Pi^1_2$ notion instead. The talk will be aimed at a general logic audience. Topics will include: proof-theoretic $\Pi^1_2$-norms, a characterization of the $\Pi^1_2$ consequences of arithmetical comprehension and related systems, $\Pi^1_2$-soundness ordinals, and the $\Pi^1_2$-Spectrum Conjecture. This is joint work with F. Pakhomov. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom: Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 23, 2022 - - - -



- - - - Tuesday, May 24, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 24, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Laurence Kirby, Brooklyn College
The winding road to mathematical independence results for PA

Advances in understanding the incompleteness of PA in the 1970s and 80s built on the work of an earlier generation in the 1930s and 40s. This talk will offer historical and personal reflections on what was known, and what was not known, by both generations of logicians.




- - - - Wednesday, May 25, 2022 - - - -



- - - - Thursday, May 26, 2022 - - - -



- - - - Friday, May 27, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 27, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties: Part II

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




Next Week in Logic at CUNY:

- - - - Monday, May 30, 2022 - - - -



- - - - Tuesday, May 31, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 31, 8pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Tin Lok Wong National University of Singapore




- - - - Wednesday, Jun 1, 2022 - - - -



- - - - Thursday, Jun 2, 2022 - - - -



- - - - Friday, Jun 3, 2022 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 25th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Tommaso Russo -- Walks on ordinals and scattered compact spaces I will present a construction of a scattered compact topological space that answered a question due to Wiesław Kubiś and Arkady Leiderman. The construction is contained in a joint paper with Petr Hájek, Jacopo Somaglia, and Stevo Todorčević. The purpose of the paper was actually to answer a problem in Banach space theory, but for the sake of the talk I will focus on the construction of the compact space and not mention Banach spaces at all. In the talk I will give a short introduction to Descriptive Topology in order to explain the setting and to motivate the construction of the example. Then I will explain how to use the combinatorics of the set of countable ordinals, in particular Todorčević's theory of walks on ordinals, for the construction of the example. P.Hájek, T.Russo, J.Somaglia, and S.Todorčević, An Asplund space with norming Markuševič basis that is not weakly compactly generated, https://doi.org/10.1016/j.aim.2021.108041 Adv. Math. 392 (2021), 108041. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Peter Holy
TITLE: Asymmetric Cut and Choose Games
DATE: 25 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.








Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu




(KGRC) Set Theory Research Seminar talks Tuesday, May 24 and WEDNESDAY, May 25

Kurt Godel Research Center
The KGRC welcomes as guests: David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for this talk will be announced later. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. Jonathan Cancino (host: Vera Fischer) visits the KGRC until May 20. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28 and gives a talk on May 25 (see below). Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28 and gives a talk on May 25, see below. Gunter Fuchs (host: Vera Fischer) visits the KGRC from June 12 to June 18 and gives a talk on June 14. Details for this talk will be announced later. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for this talk will be announced later. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 24 "Inner Models, Determinacy, and Sealing" Sandra Müller (TU Wien) Inner model theory has been very successful in connecting determinacy axioms to the existence of inner models with large cardinals and other natural hypotheses. Recent results of Larson, Sargsyan, and Trang suggest that a Woodin limit of Woodin cardinals is a natural barrier for our current methods to prove these connections. One reason for this comes from Sealing, a generic absoluteness principle for the theory of the universally Baire sets of reals introduced by Woodin. Woodin showed in his famous Sealing Theorem that in the presence of a proper class of Woodin cardinals Sealing holds after collapsing a supercompact cardinal. I will outline the importance of Sealing and discuss a new and stationary-tower-free proof of Woodin's Sealing Theorem that is based on Sargsyan's and Trang's proof of Sealing from iterability. This is joint work with Grigor Sargsyan and Bartosz Wcisło. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Set Theory Research Seminar Kurt Gödel Research Center WEDNESDAY, May 25 (Please note the unusual day and time!) "Unindexed subshifts of finite type and a connecton to Thompsons groups" Luke Elliott (U of St Andrews, Scotland, UK) I will give a brief introduction to subshifts of finite type defined by finite directed graphs. In particular I will mention a category of "digaphs and foldings" introduced by Jim Belk, Collin Bleak, and Peter Cameron which is useful for studying these systems. I will then discuss my recent work in building an analogous category in which isomorphisms don't necessarily preserve indexing and path length. This category gives us both more flexible notions of (strong) shift equivalence and a connection to automorphisms of Thompsons groups. Time and Place (Please note the unusual day and time!) Talk at 11:30am in hybrid mode, in person as well as via Zoom: Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Cross-Alps Logic Seminar (speaker: Alberto Marcone)

Cross-Alps Logic Seminar
On Friday 20.05.2022 at 16:00
Alberto Marcone (University of Udine)
will give a talk on
The transfinite Ramsey theorem

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


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This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




Next Week in Logic at CUNY:

- - - - Monday, May 23, 2022 - - - -



- - - - Tuesday, May 24, 2022 - - - -



- - - - Wednesday, May 25, 2022 - - - -



- - - - Thursday, May 26, 2022 - - - -



- - - - Friday, May 27, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 27, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties: Part II

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Laura Fontanella
TITLE: Representing ordinals in classical realizability
DATE: 18 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 18th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- Hadwiger's conjecture for infinite graphs Hadwiger's conjecture is one of the most famous unsolved problems in finite graph theory. I will talk about the infinite version of this conjecture and related results. Best, David

(KGRC) Set Theory Research Seminar talk Tuesday, May 17 and Logic Colloquium talk Thursday, May 19

Kurt Godel Research Center
The KGRC welcomes as guests: Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for the talk will be announced at a later time. Jonathan Cancino (host: Vera Fischer) visits the KGRC from May 16 to May 20. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28 and gives a talk on May 25, 11:30am (please note the unusual time!). Details for the talk will be announced at a later time. Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28. Alessandro Vignati (host: Vera Fischer) visits the KGRC from June 30 to July 1 and gives a talk on June 30. Details for the talk will be announced at a later time. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 17 "Patterns in the large cardinal hierarchy" Philipp Lücke (University of Bareclona) In my talk, I will present results showing that the existence of various well-known large cardinals can be characterized through the validity of strong extensions of the downward Löwenheim-Skolem theorem. These equivalences show that certain patterns recur throughout the large cardinal hierarchy. In particular, they show that strongly unfoldable cardinals, introduced by Villaveces in his model-theoretic investigations of models of set theory, relate to subtle cardinals, introduced by Kunen and Jensen in their studies of strong diamond principles, in the same way as supercompact cardinals relate to Vopěnka cardinals and strong cardinals relate to Woodin cardinals. This is joint work in progress with Joan Bagaria (Barcelona). Time and Place This talk will be given via Zoom. If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Logic Colloquium Kurt Gödel Research Center Thursday, May 19 "Axiomatizing Kaufmann Models of Arithmetic in Strong Logics" Corey Switzer (KGRC) A {\em Kaufmann model} of $\mathsf{PA}$ is an $\omega_1$-like, recursively saturated, rather classless model (these terms will be defined in the talk). Such models have been an important object of study in model theory of arithmetic and its environs since the 70's. Kaufmann models are natural counterexamples to several theorems about countable models of $\mathsf{PA}$ holding at the uncountable. Moreover they are a witness to incompactness at $\omega_1$ similar to an Aronszajn tree. The proof that Kaufmann models exist lies along a somewhat twisted road. Kaufmann showed that there are Kaufmann models under the combinatorial principle $\diamondsuit_{\omega_1}$ and, later, Shelah eliminated the use of $\diamondsuit_{\omega_1}$ by appealing to a forcing absoluteness argument involving the strong logic $L_{\omega_1, \omega}(Q)$ where $Q$ is the quantifier ``there exists uncountably many''. It remains an extremely interesting, if somewhat vague, question, attributed to Hodges, whether one can build a Kaufmann model ``by hand'' in $\mathsf{ZFC}$ without appealing to generic absoluteness. In this talk we will report on our recent progress in this area. Specifically we will consider the role that the strong logic $L_{\omega_1, \omega}(Q)$ plays in Kaufmann models and show that the statement ``Kaufmann models can be axiomatized by $L_{\omega_1, \omega}(Q)$'' is independent of $\mathsf{ZFC}$. Along the way we will discuss how Kaufmann models are affected by forcing and in particular show that it is independent of $\mathsf{ZFC}$ whether or not there is a Kaufmann model which can be ``killed" by forcing without collapsing $\omega_1$. Time and Place Talk at 3:00pm Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

TOMORROW: Vladimir Tkachuk at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
Lindelöf Σ-spaces in 2022 Speaker: Vladimir Tkachuk, Universidad Autónoma Metropolitana Date and Time: Friday, May 13, 2022 - 1:30pm to 3:00pm EDT (UTC -4) Location: https://zoom.us/j/92701726800 Abstract: This talk is a survey and an advertisement of the theory of Lindelöf Σ-spaces. We will present ten equivalent definitions of the Lindelöf Σ-property and a selection of results that have numerous applications in General Topology, Topological Algebra and C_p-theory. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Cross-Alps Logic Seminar (speaker: Udayan B. Darji)

Cross-Alps Logic Seminar
On Friday 13.05.2022 at 16:00
Udayan B. Darji (University of Louisville)
will give a talk on
Descriptive complexity and local entropy

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.



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UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Quick correction:  Tuesday's Models of Peano Arithmetic (MOPA) talk will take place at 10am (not 2pm). 

Sorry for the error,
Jonas


This Week in Logic at CUNY:

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 10am
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).



Next Week in Logic at CUNY:

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).



Next Week in Logic at CUNY:

- - - - Monday, May 16, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 16, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Mircea Dumitru (Bucharest)
Title: Modal Frame Incompleteness: An Account through Second Order Logic

Abstract: Propositional modal logic is usually viewed as a generalization and extension of propositional classical logic. The main argument of this paper is that a good case can be made that modal logic should be construed as a restricted form of second order classical logic. The paper makes use of the embedding of modal logic in second order logic and henceforth it goes on examining one aspect of this second order connection having to do with an incompleteness phenomenon. The leading concept is that modal incompleteness is to be explained as a kind of exemplification of standard order incompleteness. Moreover the modal incompleteness phenomenon is essentially rooted in the weaker expressive power of the language of sentential modal logic as compared to the stronger expressive power of the language of second order logic.




- - - - Tuesday, May 17, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 17, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Ken McAloon, Brooklyn College
E Pluribus Unum

Athena sprang forth full grown from the head of Zeus. Newton/Leibniz created Calculus. Galois created Galois Theory. Cantor created Set Theory. Boole created Boolean Algebra.

But Models of Peano Arithmetic doesn’t have a dramatic origin myth like that and took some 100 years to emerge as a discipline in itself - from Dedekind’s Second Order Axioms for Arithmetic (1863), through Frege’s Begriffsschrift (1879) and First Order Logic, through Godel’s Completeness and Incompleteness Theorems, through Skolem’s elegant construction of a non-standard model, through the War and après-guerre and on into the 1970s where the subject at last emerges as a discipline in itself. We’ll discuss the convergence of people and ideas from diverse fields like Model Theory, Set Theory, Recursion Theory, Proof Theory, Complexity Theory, … that led to the field we know and love today.





- - - - Wednesday, May 18, 2022 - - - -



- - - - Thursday, May 19, 2022 - - - -



- - - - Friday, May 20, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 20, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University
Determinacy and Partition Properties

In this talk, we will review some basic properties of partition cardinals under the axiom of determinacy. We will be particularly interested with the strong partition property of the first uncountable cardinal and the good coding system used to derive these partition properties. We will discuss almost everywhere behavior of functions on partition spaces of cardinals with respect to the partition measures including various almost everywhere continuity and monotonicity properties. These continuity results will be used to distinguish some cardinalities below the power set of partition cardinals. We will also use these continuity results to produce upper bounds on the ultrapower of the first uncountable cardinal by each of its partition measures, which addresses a question of Goldberg. Portions of the talk are joint work with Jackson and Trang.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 11th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino Manriquez -- Ultrafilters in the Miller model We will sketch a proof that in the Miller's model I-ultrafilters are dense in the Rudin-Blass ordering for any analytic tall p-ideal I. We will finish with some remarks to a theorem of C. Laflamme and J. P. Zhu, and some questions on cardinal invariants related to the existence of I-ultrafilters. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Sandra Müller
TITLE: Inner Models, Determinacy, and Sealing
DATE: 11 May 2022
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.





Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Wednesday, May 11: Inaugural Lecture of Matthias Aschenbrenner

Kurt Godel Research Center
The KGRC welcomes as guests: Miguel Antonio Cardona Montoya (host: Vera Fischer) visits the KGRC until May 6. Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC until May 31. David Schrittesser (host: Vera Fischer) visits the KGRC until August 31 and gives a talk on June 21. Details for the talk will be announced at a later time. James Mitchell (host: Vera Fischer) visits the KGRC from May 21 to May 28. Yann Peresse (host: Serhii Bardyla) visits the KGRC from May 21 to May 28. Luke Elliott (host: Lyubomyr Zdomskyy) visits the KGRC from May 21 to May 28. * * * Mathematisches Kolloquium Faculty of Mathematics Wednesday, May 11 Inaugural Lecture: "Hardy’s dream" Matthias Aschenbrenner (KGRC) I will introduce an algebraic approach to asymptotic analysis, which goes back to G. H. Hardy but has its roots in the 19th century, and which has found uses in real analytic geometry and dynamical systems, computer algebra, ergodic theory, and various other fields of mathematics. In the last few years, we have obtained some decisive results on solving systems of algebraic differential equations in this setting, leading to rich classes of non-oscillating differentiable real-valued functions which partially substantiate “Hardy’s dream” (Ecalle). These results are obtained through a fruitful interplay between analysis, algebra, and logic, which I will outline in this talk. (No prior knowledge of mathematical logic will be assumed.) Time and Place Coffee at 3:45pm Talk at 4:15pm in hybrid mode, in person as well as via Zoom followed by refreshments Universität Wien Fakultät für Mathematik 12th floor Sky Lounge Oskar-Morgenstern-Platz 1 1090 Wien Zoom link for Inaugural Lecture: https://univienna.zoom.us/j/65619931234?pwd=WTdKV1Z4NGxBeklkT0RtNzltZEhBUT09 (See also PDF attached to this message.)
View attachment

Mirna Dzamonja at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
Morass-generic structures Speaker: Mirna Dzamonja, IRIF - Centre national de la recherche scientifique (CNRS) - Université deParis Date and Time: Friday, May 6, 2022 - 1:30pm to 3:00pm EDT (UTC -4) Location: https://zoom.us/j/92701726800 Abstract: We discuss a joint work with Wiesław Kubiś on a specific way of constructing structures of size ℵ1 using finite approximations, namely by organising the approximations along a simplified morass. We demonstrate a connection with Fraïssé limits and show that the naturally obtained structure of size ℵ1 is homogeneous. Moreover, this is preserved under expansions, which leads us to a partial answer to a question of Bassi and Zucker. We give some examples of interesting structures constructed, such as the antimetric space of size ℵ1. Finally, we comment on the situation when one Cohen real is added. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 2, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 2, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Elia Zardini (Madrid)

Abstract: I’ll first propose an interpretation of the multiplicative/additive distinction among operators arising in a logical framework lacking the structural property of contraction (focusing mostly on the quantifiers): multiplicative operators represent interaction among their operands (with universal quantification representing totality and particular quantification representing dependence) whereas additive operators represent selection (with universal quantification representing choice and particular quantification representing chance). I’ll then argue that reflection on the behaviour of natural-language determiners points towards a very natural working hypothesis that associates: multiplicative universal affirmative with ‘every’; multiplicative particular affirmative with ‘some’; additive universal affirmative with ‘any’; additive particular affirmative with ‘a’. I’ll illustrate the fruitfulness of this hypothesis with four examples, from the epistemic, normative, attitudinal and stative domains respectively.



- - - - Tuesday, May 3, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 3, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Dino Rossegger, UC Berkeley and TU Wien
The structural complexity of models of PA

The Scott rank of a countable structure is the least ordinal  such that all automorphism orbits of the structure are definable by infinitary  formulas. Montalbán showed that the Scott rank of a structure is a robust measure of the structural and computational complexity of a structure by showing that various different measures are equivalent. For example, a structure has Scott rank  if and only if it has a  Scott sentence if and only if it is uniformly  categorical if and only if all its automorphism orbits are  infinitary definable.

In this talk we present results on the Scott rank of non-standard models of Peano arithmetic. We show that non-standard models of PA have Scott rank at least , but, other than that, there are no limits to their complexity. Given a completion  of  we give a reduction via bi-interpretability of the class of linear orders to the models of . This allows us to exhibit models of  of Scott rank  for every . In particular, every completion of  has models of high Scott rank.

This is joint work with Antonio Montalbán.



- - - - Wednesday, May 4, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Gershom Bazerman, Arista Networks.

Date and Time:     Wednesday May 4, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Classes of Closed Monoidal Functors which Admit Infinite Traversals.



- - - - Thursday, May 5, 2022 - - - -



- - - - Friday, May 6, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 6, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
James Holland Rutgers University

Weak Indestructibility and Reflection

Assuming multiple of strong cardinals, there are lots of cardinals with small degrees of strength (i.e.  that are +2-strong). We can calculate the consistency strength of these all cardinal's small degrees of strength being weakly indestructible using forcing and core model techniques in a way similar to Apter and Sargsyan's previous work. This yields some easy relations between indestructibility and Woodin cardinals, and also generalizes easily to supercompacts. I will give a proof sketches of these results.



Logic Workshop
CUNY Graduate Center, GC Room 6495
Friday, May 6, 2:00-3:30pm
Hybrid - The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Alexei Miasnikov, Stevens Institute of Technology
Rich algebraic structures and weak second order logic

“What can one describe by first-order formulas in a given algebraic structure A?” - is an old and interesting question. Of course, this depends on the structure A. For example, in a free group only cyclic subgroups (and the group itself) are definable in the first-order logic, but in a free monoid of finite rank any finitely generated submonoid is definable. An algebraic structure A is called rich if the first-order logic in A is equivalent to the weak second order logic. Surprisingly, there are a lot of interesting groups, rings, semigroups, etc., which are rich. I will discuss some of them and then describe various algebraic, geometric, and algorithmic properties that are first-order definable in rich structures and apply these to some open problems. Weak second order logic can be introduced into algebraic structures in different ways: via HF-logic, or list superstructures over A, or computably enumerable infinite disjunctions and conjunctions, or via finite binary predicates, etc. I will describe a particular form of this logic which is especially convenient to use in algebra and show how to effectively translate such weak second order formulas into the equivalent first-order ones in the case of a rich structure A.



Next Week in Logic at CUNY:

- - - - Monday, May 9, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 9, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Julian Schlöder (UConn).
Title: Neo-Pragmatism about Truth

Abstract: Deflationists about truth hold that the function of the truth predicate is to enable us to make certain assertions we could not otherwise make. Pragmatists claim that the utility of negation lies in its role in registering incompatibility. The pragmatist insight about negation has been successfully incorporated into bilateral theories of content, which take the meaning of negation to be inferentially explained in terms of the speech act of rejection. One can implement the deflationist insight in the pragmatist’s theory of content by taking the meaning of the truth predicate to be explained by its inferential relation to assertion. There are two upshots. First, a new diagnosis of the Liar, Revenges and attendant paradoxes: the paradoxes require that truth rules preserve evidence, but they only preserve commitment. Second, one straightforwardly obtains axiomatisations of several supervaluational hierarchies, answering the question of how such theories are to be naturally axiomatised. This is joint work with Luca Incurvati (Amsterdam).





- - - - Tuesday, May 10, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 10, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Saeed Salehi, University of Tabriz
ω-Consistency: Gödel’s “much weaker” notion of soundness

As the history goes, and was confirmed recently [vP20], Gödel first proved his first incompleteness theorem [G31] for sound theories (that extend Principia Mathematica). Later he weakened the soundness condition to “ℵ0-consistency”, which later evolved to “ω-consistency”. This condition was needed for irrefutability of (what is now called) Gödelian sentences; the simple consistency of a theory suffices for the unprovability of such sentences. Gödel already notes in [G31] that a necessary and sufficient condition for the independence of Gödelian sentences of T is just a bit more than the simple consistency of T: the consistency of T with ConT, the consistency statement of T.
In this talk, we ask the following questions and attempt at answering them, at least partially.

  1. Why on earth Gödel [G31] had to introduce this rather strange notion?
  2. Does it have any applications in other areas of logic, arithmetical theories, or mathematics?
  3. What was Gödel’s reason that ω-consistency is “much weaker” than soundness? He does prove in [G31] that consistency is weaker (if not much weaker) than ω-consistency; but never mentions a proof or even a hint as to why soundness is (much) stronger than ω-consistency!
  4. Other than those historical and philosophical questions, is this a useful notion worthy of further study?
We will also review some properties of ω-consistency in the talk.
References:
  • [G31]   Kurt Gödel (1931); “On formally undecidable propositions of Principia Mathematica and related systems I”, in: S. Feferman, et al. (eds.), Kurt Gödel: Collected Works, Vol. I: Publications 1929–1936, Oxford University Press, 1986, pp. 135–152.
  • [vP20]   Jan von Plato (2020); Can Mathematics Be Proved Consistent? Gödel’s Shorthand Notes & Lectures on Incompleteness, Springer.
    Reviewed in the zbMATH Open at https://zbmath.org/1466.03001




- - - - Wednesday, May 11, 2022 - - - -

Tutorial: Categorical Semantics of Entropy
Wednesday 11 May 2022, 13:00–16:30 Eastern Time, Room 5209 at the CUNY Graduate Center and via Zoom. Organized by John Terilla. 
To attend, register here.




- - - - Thursday, May 12, 2022 - - - -



- - - - Friday, May 13, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 13, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrew Brooke-Taylor University of Leeds


CONFERENCE: Categorical Semantics of Entropy
There will be a workshop on the categorical semantics of entropy at the CUNY Grad Center in Manhattan on Friday May 13th.
John Baez uc Riverside; Centre for Quantum Technologies; Topos Institute 
Tai-Danae Bradley The Master's University; Sandbox AQ
Owen Lynch Utrecht University
Tom Mainiero Rutgers New High Energy Theory Center
Arthur Parzygnat Institut des Hautes Études Scientifiques
David Spivak MIT and the Topos Instiftute
Note: There is a related tutorial taking place on May 11 (see above).


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday May 4th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Some simple applications of set theory to the study of projective and injective objects in various categories Projective and injective objects are of central interest in category theory and homological algebra. We will survey a few interesting results applying set-theoretic ideas to the study of such objects in the categories of compact Hausdorff spaces, Banach spaces, and pro-abelian groups. Time permitting, we will also discuss some recent applications of set theory to the newly developed "condensed mathematics" of Clausen and Scholze. Everything will be presented at a fairly basic level; no significant prior knowledge of either set theory or category theory/homological algebra will be required of the audience. Best, David

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All,
For the next seminar session, on May 4, please use the following link, instead of the usual one.




Apologies for the inconvenience.
Best regards,
Joan Bagaria



El 27 abr 2022, a les 18:10, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:



El 27 gen 2022, a les 21:17, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Will Boney
TITLE: Compactness of strong logics and large cardinals
DATE: 4 May 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.


<BCNSETS2022-2-Boney.pdf>

Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Barcelona Set Theory Seminar

Barcelona Logic Seminar


El 27 gen 2022, a les 21:17, Joan Bagaria <joan.bagaria@icrea.cat> va escriure:

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Will Boney
TITLE: Compactness of strong logics and large cardinals
DATE: 4 May 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Set Theory Seminar talk Tuesday, May 3

Kurt Godel Research Center
The KGRC welcomes as guests: Marta Maloid-Glebova (host: Lyubomyr Zdomskyy) visits the KGRC from May 2 to May 31. Miguel Antonio Cardona Montoya (host: Vera Fischer) visits the KGRC from May 2 to May 6 and gives a talk (see below). David Schrittesser (host: Vera Fischer) visits the KGRC from May 2 to August 31 and gives a talk on June 21. * * * For a recent session in the Set Theory Research Seminar, video has been recorded. So if you missed it or want to rewatch it, here it is: Wolfgang Wohofsky, "Fresh function spectra" https://univienna.zoom.us/rec/share/vwFTPqrhTaAiFQ69Wn2JQF_nKulP0jvSRK8W3BvInrAyigDfZjMjeV67YOPedR5X.D2QNfwj0OkvjgZID Passcode H5#My6LX * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, May 3 "On the cardinal characteristics associated with \varepsilon" Miguel Antonio Cardona Montoya (TU Wien) Let $\varepsilon$ be the $\sigma$-ideal generated by closed measure zero sets of reals. We prove that, for $\varepsilon$, their associated cardinal characteristics (i.e. additivity, covering, uniformity and cofinality) are pairwise different. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

XIX Latin American Symposium of Mathematical Logic (SLALM), Costa Rica, July 26-30

Conference
Estimado miembro de la comunidad matemática, Fecha límite extendida para recepción de charlas y pósters: 1 de Mayo del 2022. Le agradeceríamos difundir a sus colegas, estudiantes y a su Sociedad Matemática local, el anuncio del XIX Simposio Latino Americano de Lógica Matemática, el cual tendrá lugar en la, en la ciudad de San José, Costa Rica, del martes 26 al sábado 30 de Julio del 2022. Esta conferencia será presencial. Podrá encontrar más información en el siguiente vínculo: Sitio Oficial. Además, queremos notar las fechas límites: Inscripción temprana: antes 22 de abril de 2022 Inscripción: antes 30 de junio de 2022 Recepción de charlas contribuidas y pósters: 1° de Mayo, 2022 Comunicación de aceptación-rechazo a los autores: antes 16 de mayo de 2022 Cordialmente, Comité Organizador *********************************************************************************************************************************** Extended deadline for contributed talks and posters: May 1st, 2022 Dear member of the mathematical community, We would be very grateful if you could share with your colleagues, students, and you local Mathematical Society the announcement of the XIX Latin American Symposium of Mathematical Logic (SLALM), which will be held at the Universidad de Costa Rica, in the city of San José, Costa Rica, from Friday July 26th to Saturday 20th of December, 2022. You will find more information on the following link: Official website SLALM Plus, we would like to point out the following important deadlines, Early registration April 22nd, 2022 Registration: June 30th, 2022 Contributed talks: May 1st, 2022 Communication of acceptance for contributed talks: May 16th, 2022 Sincerely, Organizing Committee
Link to more info

European Set Theory Conference 2022 - second announcement

Cross-Alps Logic Seminar
EUROPEAN SET THEORY CONFERENCE 2022
August 29th-September 2nd, 2022
Turin, Italy

This is the second announcement concerning the ESTC2022. In particular, please notice that
  • The deadline for submitting an abstract is approaching (next Saturday!): if you plan to give a contributed talk, please apply here.
  • Various forms of financial support for young researchers are available. We encourage all interested students and young post-docs to apply as soon as possible.
Please share this announcement with all people who might be interested in the event (more information below or on our website).

We are looking forward to welcoming you in Turin!
Luca Motto Ros (on behalf of the organizers)

-----------------------------------------------

IMPORTANT DEADLINES:

30/04/2022: Abstract submission for contributed talks
30/06/2022: Early registration with reduced fee
22/08/2022: Registration


MORE ON THE CONFERENCE:

The European Set Theory Conferences is a series of biannual meetings coordinated by the European Set Theory Society (ESTS). This year's edition is organized by the Department of Mathematics of the University of Turin and ESTS, in partnership with the Clay Mathematics Institute. It is the most important conference in set theory, and gathers the worldwide leaders in the field as well as many young researchers. During the event, the prestigious Hausdorff medal will be awarded for the most influential work in set theory published in the preceding five years. There will also be a special session in honor of Boban Veličković's 60th birthday.

Invited speakers

- Jeffrey Bergfalk (University of Vienna)
- Filippo Calderoni (University of Illinois Chicago)
- Natasha Dobrinen (University of Denver)
- Osvaldo Guzmán (Universidad Nacional Autónoma de México)
- Joel Hamkins (University of Notre Dame)
- Chris Lambie-Hanson (Czech Academy of Sciences)
- Martino Lupini (Victoria University of Wellington)
- Julien Melleray (Université de Lyon)
- Andrew Marks (University of California, Los Angeles)
- Sandra Müller (TU Wien)
- Saharon Shelah (Hebrew University of Jerusalem)
- Stevo Todorčević (University of Toronto and Centre national de la recherche scientifique)
- Jouko Väänänen (University of Helsinki)
- Zoltán Vidnyánsky (California Institute of Technology)
- Trevor Wilson (Miami University, Oxford Ohio)

Tutorials

- Yair Hayut (Hebrew University of Jerusalem)
- Grigor Sargsyan (Polish Academy of Sciences)

Boban Veličković's 60th Birthday Celebration

- Laura Fontanella (Université Paris-Est Créteil)
- Rahman Mohammadpour (TU Wien)
- Giorgio Venturi (University of Campinas)
- Matteo Viale (University of Turin)

Scientific committee

Joan Bagaria (chair), Matthew Foreman, Moti Gitik, Péter Komjáth, Piotr Koszmider, Heike Mildenberger, Luca Motto Ros, John Steel

Local organizing committee

Alessandro Andretta, Raphaël Carroy, Luca Motto Ros, Gianluca Paolini, Francesco Parente, Salvatore Scamperti, Matteo Viale

--
Luca Motto Ros
Università degli Studi di Torino
Dipartimento di Matematica
via Carlo Alberto, 10 - 10123 Torino, Italy

office phone: (+39) 011 670 2892
fax: (+39) 011 670 2878

Matteo Viale at the Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
The (Absolute) Model Companionship Spectrum of a mathematical theory and the Continuum problem Speaker: Matteo Viale, University of Torino and University of Turin Date and Time: Friday, April 29, 2022 - 1:30pm to 3:00pm Location: https://zoom.us/j/92701726800 Abstract: We introduce a classification tool for mathematical theories based on Robinson's notion of model companionship; roughly the idea is to attach to a mathematical theory T those signatures L such that T as axiomatized in L admits a(n absolute) model companion. To do so we also introduce a slight strengthening of model companionship (absolute model companionship - AMC) which characterize those model companionable L-theories T whose model companion is axiomatized by the Π2-sentences for L which are consistent with the universal theory of any L-model of T. We use the above to analyze set theory, and we show that the above classification tools can be used to extract (surprising?) information on the continuum problem. http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar To unsubscribe, send an email to SET-THEORY-FIELDS-L-signoff-request@LISTSERV.UTORONTO.CA

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 25, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 25, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Tore Fjetland Øgaard (Bergen).
Title: Logical Suppression Anew

Abstract: Val Plumwood and Richard Sylvan argued from their joint paper The Semantics of First Degree Entailment and onward that the variable sharing property is but a mere consequence of a good entailment relation; indeed they viewed it as a mere negative test of adequacy of such a relation, the property itself being a rather philosophically barren concept. Such a relation is rather to be analyzed as a sufficiency relation free of any form of premise suppression. Suppression of premises, therefore, gained center stage. Despite this, however, no serious attempt was ever made at analyzing the concept. A first rigorous analysis of their notion of suppression was given in Farewell to Suppression-Freedom. Therein it was shown that Plumwood and Sylvan’s notion of suppression is in fact properly weaker than variable sharing. I will in the current talk explore ways of strengthening the suppression criterion. One plausible way of doing so, I will argue, yields a principle equivalent to the standard variable sharing property. I hope to show, then, that the notion of suppression is not as unfruitful as I previously made it out to be.



- - - - Tuesday, Apr 26, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 26, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Michał Godziszewski, University of Vienna
Modal Quantifiers, Potential Infinity, and Yablo sequences

When properly arithmetized, Yablo's paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but -inconsistent. Adding either uniform disquotation or the -rule results in inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn't arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is -inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back - it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the -rule. This is joint work with Rafał Urbaniak from the University of Gdańsk.




- - - - Wednesday, Apr 27, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Alex Sorokin, Northeastern University.

Date and Time:     Wednesday April 27, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     The defect of a profunctor.


Abstract: In the mid 1960s Auslander introduced a notion of the defect of a finitely presented functor on a module category. In 2021 Martsinkovsky generalized it to arbitrary additive functors. In this talk I will show how to define a defect of any enriched functor with a codomain a cosmos. Under mild assumptions, the covariant (contravariant) defect functor turns out to be a left covariant (right contravariant) adjoint to the covariant (contravariant) Yoneda embedding. Both defects can be defined for any profunctor enriched in a cosmos V. They happen to be adjoints to the embeddings of V-Cat in V-Prof. Moreover, the Isbell duals of a profunctor are completely determined by the profunctor's covariant and contravariant defects. These results are based on applications of the Tensor-Hom-Cotensor adjunctions and the (co)end calculus.



- - - - Thursday, Apr 28, 2022 - - - -



- - - - Friday, Apr 29, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 29, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan
Do these ultrafilters exist, II: not Tukey top

This is the second of two talks devoted to two properties of ultrafilters (non-principal, on omega) for which the question 'Do such ultrafilters exist?' is open. In this talk, I'll discuss the property of not being at the top of the Tukey ordering (of ultrafilters on omega). I'll start with the definition of the Tukey ordering, and I'll give an example of an ultrafilter that is 'Tukey top'. It's consistent with ZFC that some ultrafilters are not Tukey top. The examples and the combinatorial characterizations involved here are remarkably similar but not identical to examples and the characterization from the previous talk. That observation suggests some conjectures, one of which I'll disprove if there's enough time.


Next Week in Logic at CUNY:

- - - - Monday, May 2, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 2, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Elia Zardini (Madrid)



- - - - Tuesday, May 3, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, May 3, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Dino Rossegger, UC Berkeley and TU Wien
The structural complexity of models of PA

The Scott rank of a countable structure is the least ordinal  such that all automorphism orbits of the structure are definable by infinitary  formulas. Montalbán showed that the Scott rank of a structure is a robust measure of the structural and computational complexity of a structure by showing that various different measures are equivalent. For example, a structure has Scott rank  if and only if it has a  Scott sentence if and only if it is uniformly  categorical if and only if all its automorphism orbits are  infinitary definable.

In this talk we present results on the Scott rank of non-standard models of Peano arithmetic. We show that non-standard models of PA have Scott rank at least , but, other than that, there are no limits to their complexity. Given a completion  of  we give a reduction via bi-interpretability of the class of linear orders to the models of . This allows us to exhibit models of  of Scott rank  for every . In particular, every completion of  has models of high Scott rank.

This is joint work with Antonio Montalbán.



- - - - Wednesday, May 4, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Gershom Bazerman, Arista Networks.

Date and Time:     Wednesday May 4, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Classes of Closed Monoidal Functors which Admit Infinite Traversals.



- - - - Thursday, May 5, 2022 - - - -



- - - - Friday, May 6, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, May 6, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
James Holland Rutgers University
TBA


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Kacper Kucharski, Using elementary submodels in topology (continuation)

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 26.04.2022, at 13.15, room 403 Speaker: Kacper Kucharski, (MIM UW) Title: Using elementary submodels in topology (continuation) Abstact: "The talk will be focused on presenting so-called reflection results e.g., Dow's theorem: every nonmetrizable compact Hausdorff space contains a nonmetrizable subspace of cardinality ω_1" Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 27th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Rahman Mohammadpour -- How to specialise a tree with smaller approximations A tree T of height $\kappa^+$ is called special if it is $\kappa$-colorable. The natural forcing to generically specialise a branchless tree of height $\kappa^+$ uses partial specialising functions of size less than $\kappa$. The chain condition of the post has a strong correlation with a particular compactness property. By a classical result due to Baumgartner, Malitz, and Reinhardt, there is a ccc forcing notion that generically specialises a branchless tree of height $\omega_1$, as that compactness property coincides with the property of being branchless when the height of the tree is $\omega_1$. But when the height is beyond $\omega_1$, i.e., $\kappa$ is uncountable, there might be, e.g. in the constructible universe, branchless trees that are not specialisable at all. Another negative aspect of the specialising poset is its dependence on cardinal arithmetic. For example, one cannot use it to generically specialise a tree of height $\omega_2$ without collapsing the continuum onto $\omega_1$. I will review some classical and known results on the above subjects. In particular, the connection between the chain condition of the specialising poset, the cardinal arithmetic, and a compactness property. I will then show how to use models, under appropriate circumstances, as side conditions to arrange specialisation with smaller approximations in the forcing conditions. I shall first focus on the simplest case, say trees of height $\omega_2$, and hope that I give enough details of the proofs. If times permits, I will discuss a similar problem for taller trees. Best, David

TOMORROW: Asger Törnquist at 13:30 EDT

Set Theory Seminar at the Fields Institute
Toronto Set Theory Seminar @ Fields Institute ---------------------------------------------- Friday April 22, 13:30 -- 14:30 EDT (UTC -4) Asger Törnquist (University of Copenhagen) Title: The mathematics of a model of the mind in psychology. Abstract: Jens Mammen, a psychologist, has proposed a model of the human mind based on the idea that the brain organizes objects in the world into two kinds of general categories: Broad categories, which he called "sense categories", and categories of special, distinguished objects (or people), which he called "choice categories". From a mathematical point of view, it is interesting that Mammen formulated his model of the mind axiomatically, based on the notion of a topological space. The objects in the universe are modelled by the points in a topological space (U,S), where the (broad) sense categories are modelled by open sets in the topology S. The choice categories forms an additional collection of subsets of the universe, C, that together with the topology must adhere to certain axioms. The triple (U,S,C) is called a "Mammen space" (a term that I introduced). Several mathematical questions arise out Mammen's theory. For instance, if we want Mammen's model to be able to account for all possible subsets of the universe (a property Mammen called "completeness"), then the Axiom of Choice, or at least some non-trivial consequences thereof, seem to play a role. There are also several interesting questions related to cardinal invariants, such as the "weight" of the underlying topological space of a complete Mammen space. I will give an overview of the mathematics of Mammen spaces and known results, and also discuss the numerous unsolved problems that remain. location: https://zoom.us/j/92701726800 http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 18, 2022 - - - -



- - - - Tuesday, Apr 19, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 19, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Roman Kossak, CUNY
Absolute undefinability in arithmetic

I will survey some well-known and some more recent undefinability results about models of Peano Arithmetic. I want to contrast first-order undefinability in the standard model with a much stronger notion of undefinability which is suitable for resplendent models, and use the results to motivate some more general questions about the nature of undefinability.



- - - - Wednesday, Apr 20, 2022 - - - -



- - - - Thursday, Apr 21, 2022 - - - -



- - - - Friday, Apr 22, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 22, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan


Logic Workshop
CUNY Graduate Center, Friday, April 22, 2pm
In Person (contact Russell Miller by April 15 to be admitted into GC for the talk)
GC Room 5417
Jouko Väänänen University of Helsinki

Stationary logic and set theory

Stationary logic was introduced in the 1970’s. It allows the quantifier 'for almost all countable subsets s…'. Although it is undoubtedly a kind of second order logic, it is completely axiomatizable, countably compact and satisfies a kind of Downward Lowenheim-Skolem theorem. In this talk I give first a general introduction to the extension of first order logic by this 'almost all'-quantifier. As 'almost all' is interpreted as 'for a club of', the theory of this logic is entangled with properties of stationary sets. I will give some examples of this. The main reason to focus on this logic in my talk is to use it to build an inner model of set theory. I will give a general introduction to this inner model, called C(aa), or the aa-model, and sketch a proof of CH in the model. My work on the aa-model is joint work with Juliette Kennedy and Menachem Magidor.





Next Week in Logic at CUNY:

- - - - Monday, Apr 25, 2022 - - - -



- - - - Tuesday, Apr 26, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 26, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)

Michał Godziszewski, University of Vienna
Modal Quantifiers, Potential Infinity, and Yablo sequences

When properly arithmetized, Yablo's paradox results in a set of formulas which (with local disquotation in the background) turns out to be consistent, but -inconsistent. Adding either uniform disquotation or the -rule results in inconsistency. Since the paradox involves an infinite sequence of sentences, one might think that it doesn't arise in finitary contexts. We study whether it does. It turns out that the issue depends on how the finitistic approach is formalized. On one of them, proposed by Marcin Mostowski, all the paradoxical sentences simply fail to hold. This happens at a price: the underlying finitistic arithmetic itself is -inconsistent. Finally, when studied in the context of a finitistic approach which preserves the truth of standard arithmetic, the paradox strikes back - it does so with double force, for now the inconsistency can be obtained without the use of uniform disquotation or the -rule. This is joint work with Rafał Urbaniak from the University of Gdańsk.




- - - - Wednesday, Apr 27, 2022 - - - -



- - - - Thursday, Apr 28, 2022 - - - -



- - - - Friday, Apr 29, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 29, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan




- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

CMU seminars this week (logic, model theory, set theory)

Carnegie Mellon Logic Seminar
TUESDAY, April 19, 2022 Mathematical logic seminar: 3:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part I) ABSTRACT: The notion of abstract elementary classes (AECs) is an axiomatic framework developed by Shelah to generalize classification theory beyond the first-order context. One central test question is the categoricity conjecture: if an AEC K is categorical in some $\mu\geq\beth_{(2^{LS(K)})^+}$, then it is categorical in all $\mu\geq\beth_{(2^{LS(K)})^+}$. After going through the axioms of AECs, we will overview some partial results in the literature, in particular those assuming tameness, type-shortness and the amalgamation property. We show that: assuming type-shortness and amalgamation over sets, the categoricity conjecture is true. Our result also provides an alternative proof to the upward categoricity transfer in first-order theories. TUESDAY, April 19, 2022 Set Theory Seminar: 4:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part II) ABSTRACT: We will look at the main tools used in the proof of our categoricity transfer: good frames, multidimensional diagrams and primes. It is known that our assumptions allow a set-theoretic argument to transfer categoricity down to $\beth_{(2^{LS(K)})^+}$. We will discuss examples that encode the cumulative hierarchy, which have the first categoricity cardinals up to $\beth_{(2^{LS(K)})^+}$, but fail amalgamation. We conjecture that a more refined set-theoretic construction might provide such examples that also satisfy amalgamation, which will imply the above threshold is tight. THURSDAY, April 21, 2022 Model Theory Seminar: 11:00 A.M., Online, T. G. Kucera, University of Manitoba, Canada Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Saturated free algebras and almost indiscernible theories: an overview ABSTRACT: This is work motivated by questions at the intersection of algebra and model theory, and using advanced techniques of model theory. Baldwin and Shelah (Algebra Universalis, 1983) studied saturated free algebras. Pillay and Sklinos (Bull. Symb. Logic 2015), following the lead of this paper, studied "almost indiscernible theories", taking the opportunity to refine the statements of the major results and improve the proofs. We extend these results to large infinite contexts, both in the size of the language and the kinds of tuples allowed in an indiscernible set, and return to examples and applications in algebra, in particular in the theory of modules. The theory develops by noting various analogies. The idea of 'indiscernible sequence' generalizes various kinds of independence in algebra, including 'linearly independent set' in a vector space, 'free (generating) set' of an algebra, 'algebraic independence' in an algebraically closed field, and similar concepts. 'Saturated model' generalizes concepts such as 'injective envelope of a module', 'algebraic closure of a field', and similar constructions. A complete theory is "almost indiscernible" if it has a (sufficiently large) saturated model which lies in the algebraic closure of an indiscernible set (of sequences). Requiring that a saturated model be generated by an indiscernible set imposes strong structural constraints, but nonetheless there are natural motivating examples. This will be a talk without proofs. If there is sufficient interest I can return at a later time to cover the proofs of the main model-theoretic results. I start with some history and motivation from algebra, and then introduce our extension of the definition of an "almost indiscernible theory". I will give a summary of the main results, in particular that such a theory T is superstable, stable in |T|, and non-multi-dimensional. I'll only mention briefly the main tools of the proofs. Then I will present some consequences for free algebras and for theories of modules, including structure theorems and some examples. I conclude with a list of open questions. This is joint work with Anand Pillay Article link: https://link.springer.com/article/10.1007/s00012-021-00766-x

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Claudio Agostini -- On some extensions of theorems in combinatorics Ramsey monoids have been introduced by Solecki in 2019 to generalize and extend famous theorems in combinatorics such as Hindman’s theorem, Carlson’s Theorem on variable words, and Gowers’ $\mathrm{FIN}_k$ Theorem. In short, a monoid is Ramsey if for every action of the monoid on a semigroup and for any finite coloring of the semigroup there is an infinite monochromatic ``nice set'' closed to a certain degree under the operation of the semigroup and the action of the monoid. Relaxing or strengthening the requirements that the ``nice set'' must satisfies, one can obtain other classes of monoids, like $\mathbb{Y}$-controllable monoids, locally Ramsey monoids and locally $\mathbb{Y}$-controllable monoids. In this talk, I will introduce these notions and discuss some recent progress in the study of these classes. This is a joint work with Eugenio Colla. Best, David

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 13th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Chodounsky -- Colors of the pseudotree The pseudotree is the Fraisse limit of the class of finite trees with embeddings which respect the meet operation. In this short talk I will cover the little we know about the big Ramsey degrees of substructures of the pseudotree. This is joint work Monroe Eskew and Thilo Weinert. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 11, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 11, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Justin Bledin (Johns Hopkins)
Title: From Truthmaker to Menu Semantics

Abstract: The logical foundations of English and other natural languages are often assumed to have an essentially truth-theoretic character where the meanings of connectives and quantifiers are grounded in the truth and falsity of sentences. In this talk, I explore a fundamentally different perspective that shifts the focus from the truth value to the ‘menu’. Under this alternative conception of the logic of natural language, speakers manifest their logical competence by, metaphorically speaking, constructing and combining menus of items in various types throughout the grammar. The logical connectives are ‘menu constructors’: negation can be used to express that items are ‘off’ the menu, conjunction produces combinations of ‘on-menu’ items, and disjunction introduces choice between items. My point of departure for this truth displacing project is, oddly enough, recent work in ‘truthmaker’ or ‘exact’ semantics. What I try to do is build a bridge between the standard theory of truthmaker semantics (van Fraassen 1969; Fine 2017), which assigns menus of truthmakers and falsemakers at the sentential level, and compositional semantics in the general style of Montague. One of the most striking aspects of the theory is its treatment of noun phrases, as both quantificational and non-quantificational NPs are all assigned both denotations and ‘anti-denotations’ drawn or constructed from a rich entity space populated by both positive and negative individuals and their sums. Towards the end of the talk, I will try to bring out the explanatory power of menu semantics by applying it to a couple of problem areas in natural language quantification.




- - - - Tuesday, Apr 12, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 12, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Thomas Ferguson University of Amsterdam and University of St. Andrews




- - - - Wednesday, Apr 13, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Alex Martsinkovsky, Northeastern University.
Date and Time:     Wednesday April 13, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     A Reflector in Search of a Category.

Abstract: The last several months have seen an explosive growth of activities centered around the defect of a finitely presented functor. This notion made its first appearance in M. Auslander's fundamental work on coherent functors in the mid-1960s, although at that time it was mostly used just as a technical tool. A phenomenological study of that concept was initiated by Jeremy Russell in 2016. What transpired in the recent months is the ubiquitous nature of the defect, explained in part by the fact that it is adjoint to the Yoneda embedding. Thus any branch of mathematics, computer science, physics, or any applied science that references the Yoneda embedding automatically becomes a candidate for applications of the defect.

In this expository talk I will first give a streamlined introduction to the original notion of defect of a finitely presented functor defined on a module category and then show how to generalize it to arbitrary additive functors. Along the way I will give a dozen or so examples illustrating various use cases for the defect. The ultimate goal of this lecture is to provide a background for the upcoming talk of Alex Sorokin, who will report on his vast generalization of the defect to arbitrary profunctors enriched in a cosmos.

This presentation is based on joint work in progress with Jeremy Russell.




- - - - Thursday, Apr 14, 2022 - - - -



- - - - Friday, Apr 15, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 15, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Joel David Hamkins, Notre Dame University

The surprising strength of reflection in second-order set theory with abundant urelements

I shall give a general introduction to urelement set theory and the role of the second-order reflection principle in second-order urelement set theory GBCU and KMU. With the abundant atom axiom, asserting that the class of urelements greatly exceeds the class of pure sets, the second-order reflection principle implies the existence of a supercompact cardinal in an interpreted model of ZFC. The proof uses a reflection characterization of supercompactness: a cardinal  is supercompact if and only if for every second-order sentence true in some structure  (of any size) is also true in a first-order elementary substructure  of size less than . This is joint work with Bokai Yao. http://jdh.hamkins.org/surprising-strength-of-reflection-with-abundant-urelements-cuny-set-theory-seminar-april-2022



Next Week in Logic at CUNY:

- - - - Monday, Apr 18, 2022 - - - -



- - - - Tuesday, Apr 19, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 19, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Roman Kossak, CUNY
Absolute undefinability in arithmetic

I will survey some well-known and some more recent undefinability results about models of Peano Arithmetic. I want to contrast first-order undefinability in the standard model with a much stronger notion of undefinability which is suitable for resplendent models, and use the results to motivate some more general questions about the nature of undefinability.



- - - - Wednesday, Apr 20, 2022 - - - -



- - - - Thursday, Apr 21, 2022 - - - -



- - - - Friday, Apr 22, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 22, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass University of Michigan


Logic Workshop
CUNY Graduate Center, Friday, April 22, 2pm
In-person only: CUNY Graduate Center Room 6496
Jouko Väänänen University of Helsinki



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Upcoming seminars (logic, model theory, set theory)

Carnegie Mellon Logic Seminar
TUESDAY, April 12, 2022 Mathematical logic seminar: 3:30 P.M., Online, Garrett Ervin, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Filter flows ABSTRACT: A directed hypergraph G consists of a vertex set V along with a collection of directed hyperedges (A, B), where A and B are finite subsets of V. Given a set of vertices X, we think of the edge (A, B) as being on the boundary of X if X intersects A and does not completely contain B. We can generalize the notion of directed hypergraph as follows. A _filter graph_ G consists of an infinite vertex set V along with a collection of edges (F, G), where F and G are filters on V. Given a set of vertices X, we think of the edge (F, G) as being on the boundary of X if X is F-positive and the complement of X is G-positive. Filter graphs seem to be surprisingly graph-like. We'll show in this talk that filter graphs satisfy the natural generalization of the max-flow/min-cut theorem, where point masses flowing along directed edges in the usual hypergraph setting are replaced by ultrafilters flowing along filter-edges. TUESDAY, April 19, 2022 Mathematical logic seminar: 3:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part I) ABSTRACT: The notion of abstract elementary classes (AECs) is an axiomatic framework developed by Shelah to generalize classification theory beyond the first-order context. One central test question is the categoricity conjecture: if an AEC K is categorical in some $\mu\geq\beth_{(2^{LS(K)})^+}$, then it is categorical in all $\mu\geq\beth_{(2^{LS(K)})^+}$. After going through the axioms of AECs, we will overview some partial results in the literature, in particular those assuming tameness, type-shortness and the amalgamation property. We show that: assuming type-shortness and amalgamation over sets, the categoricity conjecture is true. Our result also provides an alternative proof to the upward categoricity transfer in first-order theories. TUESDAY, April 19, 2022 Set Theory Reading Group: 4:30 P.M., Online, Samson Leung, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Categoricity results of abstract elementary classes (Part II) ABSTRACT: We will look at the main tools used in the proof of our categoricity transfer: good frames, multidimensional diagrams and primes. It is known that our assumptions allow a set-theoretic argument to transfer categoricity down to $\beth_{(2^{LS(K)})^+}$. We will discuss examples that encode the cumulative hierarchy, which have the first categoricity cardinals up to $\beth_{(2^{LS(K)})^+}$, but fail amalgamation. We conjecture that a more refined set-theoretic construction might provide such examples that also satisfy amalgamation, which will imply the above threshold is tight. THURSDAY, April 21, 2022 Model Theory Seminar: 11:00 A.M., Online, T. G. Kucera, University of Manitoba, Canada Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Saturated free algebras and almost indiscernible theories: an overview ABSTRACT: This is work motivated by questions at the intersection of algebra and model theory, and using advanced techniques of model theory. Baldwin and Shelah (Algebra Universalis, 1983) studied saturated free algebras. Pillay and Sklinos (Bull. Symb. Logic 2015), following the lead of this paper, studied "almost indiscernible theories", taking the opportunity to refine the statements of the major results and improve the proofs. We extend these results to large infinite contexts, both in the size of the language and the kinds of tuples allowed in an indiscernible set, and return to examples and applications in algebra, in particular in the theory of modules. The theory develops by noting various analogies. The idea of 'indiscernible sequence' generalizes various kinds of independence in algebra, including 'linearly independent set' in a vector space, 'free (generating) set' of an algebra, 'algebraic independence' in an algebraically closed field, and similar concepts. 'Saturated model' generalizes concepts such as 'injective envelope of a module', 'algebraic closure of a field', and similar constructions. A complete theory is "almost indiscernible" if it has a (sufficiently large) saturated model which lies in the algebraic closure of an indiscernible set (of sequences). Requiring that a saturated model be generated by an indiscernible set imposes strong structural constraints, but nonetheless there are natural motivating examples. This will be a talk without proofs. If there is sufficient interest I can return at a later time to cover the proofs of the main model-theoretic results. I start with some history and motivation from algebra, and then introduce our extension of the definition of an "almost indiscernible theory". I will give a summary of the main results, in particular that such a theory T is superstable, stable in |T|, and non-multi-dimensional. I'll only mention briefly the main tools of the proofs. Then I will present some consequences for free algebras and for theories of modules, including structure theorems and some examples. I conclude with a list of open questions. This is joint work with Anand Pillay Article link: https://link.springer.com/article/10.1007/s00012-021-00766-x THURSDAY, April 28, 2022 Model Theory Seminar: 11:00 A.M., Online, Jonathan Kirby, The University of East Anglia Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Independence Relations for Exponential Fields ABSTRACT: In classical first-order logic, the presence of an independence relation on models of a complete theory T can be used to show that T is strongly minimal, stable, simple, or NSOP_1. Something analogous works in various generalisations of first-order logic, including AECs. In this talk I will illustrate the general principle by constructing various independence relations on exponential fields, that is, fields equipped with a homomorphism from their additive group to their multiplicative group, like the usual real and complex exponential maps. These independence relations can be used to prove that various AECs of exponential fields are quasiminimal, stable, or NSOP_1. In some of the stable cases, there are open questions around extending from the countable models, which are well-understood, to the uncountable ones. This is joint work with Levon Haykazyan, Robert Henderson, Mark Kamsma, and Vahagn Aslanyan.

Logic Seminar 13 April 2022 16:00 hrs at NUS by Wang Wei, Sun Yatsen University

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 13 April 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wang Wei Title: Ackermann, Ramsey and Trees URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Recently, Chong, Yang and I prove that a version of Pigeonholes Principle for trees (TT^1) is Pi^0_3-conservative over RCA_0. So, TT^1 does not imply the totality of Ackermann function over RCA_0, like the instance of Ramsey's Theorem for 2-colorings of pairs. To fit the trend of logic talks, I am not going to present many details. Instead, I will try to recall some stories about the Ackermann function and its appearance in reverse mathematics.

Logic Seminar 6 April 2022 16:00 hrs by Frank Stephan, NUS

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 6 April 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Frank Stephan Title: Matching Regular Pumping Lemmas and Automaticity Abstract: The talk investigates which versions of the pumping lemma are matching where matching means that exactly the regular languages satisfy it. In particular it will be shown that two-sided pumping lemmas where an automatic function computes the pump tend to be matching. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Cross-Alps Logic Seminar (speaker: Alexander S. Kechris)

Cross-Alps Logic Seminar
On Friday 08.04.2022 at 16:00 CEST
Alexander S. Kechris (Caltech)
will give a talk on
Countable sections for actions of locally compact groups

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


Mail priva di virus. www.avast.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 4, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 4, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Jenn McDonald (Columbia)
Title: Causal Relativism

Abstract: In this talk, I defend a kind of causal relativism. I argue that actual causation cannot be taken to hold simpliciter between two particular things (‘things’ such as events, states-of-affairs, etc.).  Instead, actual causation holds only relative to a background space of possibilities – a modal profile.  The argument applies generally to any difference-making analysis of actual causation.  But I will use the framework of structural equation models to make the case.   I first demonstrate that structural equation models represent situations in this way – as relative to some modal profile or other.  This observation is underappreciated in the literature.  I show how it raises a problem for all extant analyses of actual causation in terms of these models.  This problem is best responded to by a kind of causal relativism, or so I will argue.  Notably, the problem cannot be avoided by rejecting a structural equation framework.  While the framework is useful for its illustration, the problem arises for any analysis governed by the idea that a cause is what makes a difference in an effect’s occurrence.




- - - - Tuesday, Apr 5, 2022 - - - -



- - - - Wednesday, Apr 6, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Jason Parker, Brandon University in Manitoba.

Date and Time:     Wednesday April 6, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities.


Abstract: Several structure-semantics adjunctions and monad-theory equivalences have been established in category theory. Lawvere (1963) developed a structure-semantics adjunction between Lawvere theories and tractable Set-valued functors, which was subsequently generalized by Linton (1969), while Dubuc (1970) established a structure-semantics adjunction between V-theories and tractable V-valued V-functors for a symmetric monoidal closed category V. It is also well known (and due to Linton) that there is an equivalence between Lawvere theories and finitary monads on Set. Generalizing this result, Lucyshyn-Wright (2016) established a monad-theory equivalence for eleutheric systems of arities in arbitrary closed categories. Building on earlier work by Nishizawa and Power, Bourke and Garner (2019) subsequently proved a general monad-theory equivalence for arbitrary small subcategories of arities in locally presentable enriched categories. However, neither of these equivalences generalizes the other, and there has not yet been a general treatment of enriched structure-semantics adjunctions that specializes to those established by Lawvere, Linton, and Dubuc.

Motivated by these considerations, we develop a general axiomatic framework for studying enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities, which generalizes all of the aforementioned results and also provides substantial new examples of relevance for topology and differential geometry. For a subcategory of arities J in a V-category C over a symmetric monoidal closed category V, Linton’s notion of clone generalizes to provide enriched notions of J-theory and J-pretheory, which were also employed by Bourke and Garner (2019). We say that J is amenable if every J-theory admits free algebras, and is strongly amenable if every J-pretheory admits free algebras. If J is amenable, then we obtain an idempotent structure-semantics adjunction between certain J-pretheories and J-tractable V-categories over C, which yields an equivalence between J-theories and J-nervous V-monads on C. If J is strongly amenable, then we also obtain a rich theory of presentations for J-theories and J-nervous V-monads. We show that many previously studied subcategories of arities are (strongly) amenable, from which we recover the aforementioned structure-semantics adjunctions and monad-theory equivalences. We conclude with the result that any small subcategory of arities in a locally bounded closed category is strongly amenable, from which we obtain structure-semantics adjunctions and monad-theory equivalences in (e.g.) many convenient categories of spaces.

Joint work with Rory Lucyshyn-Wright.




- - - - Thursday, Apr 7, 2022 - - - -



- - - - Friday, Apr 8, 2022 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Apr 11, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 11, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Justin Bledin (Johns Hopkins)
Title: From Truthmaker to Menu Semantics

Abstract: The logical foundations of English and other natural languages are often assumed to have an essentially truth-theoretic character where the meanings of connectives and quantifiers are grounded in the truth and falsity of sentences. In this talk, I explore a fundamentally different perspective that shifts the focus from the truth value to the ‘menu’. Under this alternative conception of the logic of natural language, speakers manifest their logical competence by, metaphorically speaking, constructing and combining menus of items in various types throughout the grammar. The logical connectives are ‘menu constructors’: negation can be used to express that items are ‘off’ the menu, conjunction produces combinations of ‘on-menu’ items, and disjunction introduces choice between items. My point of departure for this truth displacing project is, oddly enough, recent work in ‘truthmaker’ or ‘exact’ semantics. What I try to do is build a bridge between the standard theory of truthmaker semantics (van Fraassen 1969; Fine 2017), which assigns menus of truthmakers and falsemakers at the sentential level, and compositional semantics in the general style of Montague. One of the most striking aspects of the theory is its treatment of noun phrases, as both quantificational and non-quantificational NPs are all assigned both denotations and ‘anti-denotations’ drawn or constructed from a rich entity space populated by both positive and negative individuals and their sums. Towards the end of the talk, I will try to bring out the explanatory power of menu semantics by applying it to a couple of problem areas in natural language quantification.




- - - - Tuesday, Apr 12, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, April 12, 2pm
Virtual (email Victoria Gitman vgitman@nylogic.org for meeting id)
Thomas Ferguson University of Amsterdam and University of St. Andrews




- - - - Wednesday, Apr 13, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Alex Martsinkovsky, Northeastern University.
Date and Time:     Wednesday April 13, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     A Reflector in Search of a Category.

Abstract: The last several months have seen an explosive growth of activities centered around the defect of a finitely presented functor. This notion made its first appearance in M. Auslander's fundamental work on coherent functors in the mid-1960s, although at that time it was mostly used just as a technical tool. A phenomenological study of that concept was initiated by Jeremy Russell in 2016. What transpired in the recent months is the ubiquitous nature of the defect, explained in part by the fact that it is adjoint to the Yoneda embedding. Thus any branch of mathematics, computer science, physics, or any applied science that references the Yoneda embedding automatically becomes a candidate for applications of the defect.

In this expository talk I will first give a streamlined introduction to the original notion of defect of a finitely presented functor defined on a module category and then show how to generalize it to arbitrary additive functors. Along the way I will give a dozen or so examples illustrating various use cases for the defect. The ultimate goal of this lecture is to provide a background for the upcoming talk of Alex Sorokin, who will report on his vast generalization of the defect to arbitrary profunctors enriched in a cosmos.

This presentation is based on joint work in progress with Jeremy Russell.




- - - - Thursday, Apr 14, 2022 - - - -



- - - - Friday, Apr 15, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:15pm
In-person: GC Room 6496
Virtual: Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Joel David Hamkins Notre Dame University



- - - - Other Logic News - - - -

CONFERENCE ANNOUNCEMENT:
Logic4Peace: fundraising online Logic event for Peace
University of Amsterdam
Dates: 22 and 23 April 2022
Venue: online (information will be provided to registered participants)

Logicians participating in this conference stand united for Peace. The on-going Russian military invasion in Ukraine is causing death, destruction and it is the direct cause of a gigantic humanitarian crisis. Educational facilities have been hit, supply chains have been broken and people have lost their families and homes. By organizing this conference, we offer our moral and financial support to our colleagues in Ukraine in this time of war.




- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Damian Sobota, Measures with the Additive Property and the random forcing

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 5.04.2022, at 13.15, room 403 Speaker: Damian Sobota, (KGRC Vienna) Title: Measures with the Additive Property and the random forcing Abstact: "Let μ be a finitely additive probability measure on ω which vanishes on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is not σ-additive, however it may be almost σ-additive in the following weak sense. We say that μ has the Additive Property, (AP) in short, if for every sequence (A_n) of pairwise disjoint subsets of ω there is a subset A such that A_n\A is finite for every n∈ω and μ(A)=Σ_n μ(A_n). Equivalently, for every decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n is finite for every n∈ω and μ(A)=lim_n μ(A_n). The latter definition implies immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the one-point measure δ_U has (AP). And similarly as in the case of P-points the existence of measures with (AP) is independent of ZFC. During my talk I will discuss basic properties of (families of) measures with (AP) as well as show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic measure with (AP) in the random model. The latter result implies that in this model there exists a ccc P-set in ω*, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Next math logic seminar on Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, April 5, 2022 Mathematical logic seminar: 3:30 P.M., Online, Benjamin Siskind, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: An update on order-preserving Martin's Conjecture ABSTRACT: Martin's Conjecture is a way of codifying a phenomenon observed in computability theory: the only natural functions on the Turing degrees seem to be the constant functions, the identity, and the transfinite iterates of the Turing jump. While the full conjecture is wide open, there has been significant progress on order-preserving Martin's Conjecture--that is, Martin's Conjecture restricted to the functions which preserve Turing-reducibility. In particular, the order-preserving version has been settled positively for Borel functions whereas Martin's Conjecture for even low-level Borel functions is open. In this talk, we'll discuss a plan for pushing order-preserving Martin's Conjecture beyond Borel functions involving some AD combinatorics, higher recursion theory, and forcing. This is joint, in-progress work with Patrick Lutz.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday April 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jinřich Zapletal -- Pairs of generic extensions I will present several natural variations of the notion of mutual genericity for forcing extensions, show how to produce interesting examples, and use them for consistency results in choiceless set theory. Best, David

(KGRC) Set Theory Research Seminar talk on Tuesday, April 5

Kurt Godel Research Center
Set Theory Research Seminar Kurt Gödel Research Center Tuesday, April 5 "Fresh function spectra" Wolfgang Wohofsky (KGRC) My talk will be about the notion of fresh function and I will discuss the corresponding spectrum. A function with domain lambda is fresh if it is new but all its initial segments are in the ground model. I will give general facts how to compute the fresh function spectrum, also discussing what sets are realizable as a fresh function spectrum of a forcing. Moreover, I will provide several examples, including well-known tree forcings on omega such as Sacks, Laver, Miller, and Mathias forcing, as well as Prikry and Namba forcing to illustrate the difference between fresh functions and fresh subsets. This is joint work with Vera Fischer and Marlene Koelbing. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universität Wien Institut für Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This Friday April 1, 13:30 (EDT, GMT -4) Philipp Schlicht will give a talk at the Toronto Set Theory Seminar @ The Fields Institute Title: Dichotomies for open directed hypergraphs on generalised Baire spaces Abstract: The open graph dichotomy for a subset X of the Baire space states that any open graph on X either contains a large complete subgraph or admits a countable colouring. It is a definable version of the open colouring axiom for X and generalises the perfect set property. Recently, this was generalised to infinite dimensions by Miller, Carroy and Soukup. I will discuss extensions of this result to generalised Baire spaces and a number of applications such as variants of the Hurewicz dichotomy, the determinacy of Väänänen's game and the asymmetric Baire property. This is a joint project with Dorottya Sziraki. Location: https://zoom.us/j/92701726800

Cross-Alps Logic Seminar (speaker: David Evans)

Cross-Alps Logic Seminar
On Friday 01.04.2022 at 16:00
David Evans (Imperial College London)
will give a talk on
Amalgamation properties in measured structures

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.
The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.



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This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dongwoo Kim (CUNY).
Title: Necessity, Essence and Explanation

Abstract: I shall discuss some of the relations between metaphysical modality, essence and explanation. The essentialist approach to metaphysical modality seeks to give an account of necessity (and thus of possibility) as having its source in essence. But what is essence, and in what sense and how does it give rise to necessity? In their recent paper “Essential Properties are Super-Explanatory: Taming Metaphysical Modality” (2020), Marion Godman, Antonella Mallozzi and David Papineau have attempted to address these issues with respect to aposteriori necessities concerning kinds. According to their account, the essence of a kind consists in the super-explanatory property—a single property that is causally responsible for a multitude of commonalities shared by the instances of the kind. And they argue that this super-explanatory notion of essence offers a principled account of aposteriori necessities concerning kinds. In this talk, I am going to argue that their account is not satisfactory. I shall examine two main arguments of GMP that the super-explanatory property of a kind is metaphysically necessary and argue that they both are fallacious. Along the way, a general problem will emerge that applies to any account that tries to explicate the notion of essence in terms of an explanatory relation.





- - - - Tuesday, Mar 29, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Erez Shochat, St. Francis College
A Survey on the Automorphism Groups of Countable (Boundedly) Recursively Saturated Models of PA

In this talk we discuss important results concerning the automorphism groups of countable recursively saturated models of PA and automorphism groups of the countable boundedly recursively saturated models of PA which are short (aka short recursively saturated models). We compare and contrast and also list some open questions.




- - - - Wednesday, Mar 30, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Morgan Rogers, Universit`a degli Studi dell’Insubria.

Date and Time:     Wednesday March 30, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Toposes of Topological Monoid Actions.


Abstract: Anyone encountering topos theory for the first time will be familiar with the fact that the category of actions of a monoid on sets is a special case of a presheaf topos. It turns out that if we equip the monoid with a topology and consider the subcategory of continuous actions, the result is still a Grothendieck topos. It is possible to characterize such toposes in terms of their points, and along the way extract canonical representing topological monoids, the complete monoids. I'll sketch the trajectory of this story, present some positive and negative results about Morita-equivalence of topological monoids, and explain how one can extract a semi-Galois theory from this set-up.



- - - - Thursday, Mar 31, 2022 - - - -



- - - - Friday, Apr 1, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna



Next Week in Logic at CUNY:

- - - - Monday, Apr 4, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 4, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Jenn McDonald (Columbia)
Title: Causal Relativism

Abstract: In this talk, I defend a kind of causal relativism. I argue that actual causation cannot be taken to hold simpliciter between two particular things (‘things’ such as events, states-of-affairs, etc.).  Instead, actual causation holds only relative to a background space of possibilities – a modal profile.  The argument applies generally to any difference-making analysis of actual causation.  But I will use the framework of structural equation models to make the case.   I first demonstrate that structural equation models represent situations in this way – as relative to some modal profile or other.  This observation is underappreciated in the literature.  I show how it raises a problem for all extant analyses of actual causation in terms of these models.  This problem is best responded to by a kind of causal relativism, or so I will argue.  Notably, the problem cannot be avoided by rejecting a structural equation framework.  While the framework is useful for its illustration, the problem arises for any analysis governed by the idea that a cause is what makes a difference in an effect’s occurrence.




- - - - Tuesday, Apr 5, 2022 - - - -



- - - - Wednesday, Apr 6, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Jason Parker, Brandon University in Manitoba.

Date and Time:     Wednesday April 6, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities.


Abstract: Several structure-semantics adjunctions and monad-theory equivalences have been established in category theory. Lawvere (1963) developed a structure-semantics adjunction between Lawvere theories and tractable Set-valued functors, which was subsequently generalized by Linton (1969), while Dubuc (1970) established a structure-semantics adjunction between V-theories and tractable V-valued V-functors for a symmetric monoidal closed category V. It is also well known (and due to Linton) that there is an equivalence between Lawvere theories and finitary monads on Set. Generalizing this result, Lucyshyn-Wright (2016) established a monad-theory equivalence for eleutheric systems of arities in arbitrary closed categories. Building on earlier work by Nishizawa and Power, Bourke and Garner (2019) subsequently proved a general monad-theory equivalence for arbitrary small subcategories of arities in locally presentable enriched categories. However, neither of these equivalences generalizes the other, and there has not yet been a general treatment of enriched structure-semantics adjunctions that specializes to those established by Lawvere, Linton, and Dubuc.

Motivated by these considerations, we develop a general axiomatic framework for studying enriched structure-semantics adjunctions and monad-theory equivalences for subcategories of arities, which generalizes all of the aforementioned results and also provides substantial new examples of relevance for topology and differential geometry. For a subcategory of arities J in a V-category C over a symmetric monoidal closed category V, Linton’s notion of clone generalizes to provide enriched notions of J-theory and J-pretheory, which were also employed by Bourke and Garner (2019). We say that J is amenable if every J-theory admits free algebras, and is strongly amenable if every J-pretheory admits free algebras. If J is amenable, then we obtain an idempotent structure-semantics adjunction between certain J-pretheories and J-tractable V-categories over C, which yields an equivalence between J-theories and J-nervous V-monads on C. If J is strongly amenable, then we also obtain a rich theory of presentations for J-theories and J-nervous V-monads. We show that many previously studied subcategories of arities are (strongly) amenable, from which we recover the aforementioned structure-semantics adjunctions and monad-theory equivalences. We conclude with the result that any small subcategory of arities in a locally bounded closed category is strongly amenable, from which we obtain structure-semantics adjunctions and monad-theory equivalences in (e.g.) many convenient categories of spaces.

Joint work with Rory Lucyshyn-Wright.




- - - - Thursday, Apr 7, 2022 - - - -



- - - - Friday, Apr 8, 2022 - - - -







- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Kacper Kucharski, Using elementary submodels in topology

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 29.03.2022, at 13.15, room 403 Speaker: Kacper Kucharski, (MIM UW) Title: Using elementary submodels in topology Abstact: "The main goal of the talk is to present proofs of interesting topological theorems using elementary submodels. One theorem will be the classical Arhangel'skii's result which says that the cardinality of a compact Hausdorff first countable space is at most the continuum. The second part of the talk will be focused on presenting so-called reflection results e.g., Dow's theorem: every nonmetrizable compact Hausdorff space contains a nonmetrizable subspace of cardinality ω_1" Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 30th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Ziemowit Kostana -- Games played with diamonds Parametrized diamonds are combinatorial principles that imply many consequences of the original Jensen's Diamond, yet are consistent with the CH failing. Informally speaking, they are in similar relation to Jensen's Diamond, as cardinal invariants of the Cichoń's diagram are to CH. The modern framework for these axioms was described by Dzamonja, Hrusak, and ... I would like to show that some equivalent, or "almost-equivalent", axioms can be formulated in a completely different, game-theoretic, language. This gives additional insight on how these axioms affect the universe of sets. Best, David

Logic Seminar Wednesday 30 March 2022 16:00 hrs at NUS by Wu Liuzhen

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 30 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wu Liuzhen Title: Continuum function and strongly compact cardinal URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The continuum function is a key and long-studied object inside set theory. We will survey the study on the behavior of continuum function in presence of strongly compact cardinals. We will also introduce some major research problems in this area. Finally, We discuss our recent work on forcing continuum function of some special pattern.

(KGRC) seminar talks Tuesday, March 29 and Thursday, March 31

Kurt Godel Research Center
For the two most recent sessions in the Set Theory Research Seminar, video has been recorded. So if you missed them or want to rewatch them, here they are: Jeffrey Bergfalk, "A family of higher dimensional partition principles" https://univienna.zoom.us/rec/share/iYgs9rLaHvrhRtdXzF4Swr31cGn0kZZchw0Qp_GBFWkV2h2P1k-NThPDZ2y43-GO.SQrJ2KqoAMvNPG91 Passcode vN70.uy1 Stefan Hoffelner, "Forcing the \Pi^1_n-uniformization property" https://univienna.zoom.us/rec/share/4AI5rQ3rTJTGyOFwTZXvdCb2T3pPC4nBwBLuXZSFvctbA_b4U4wuuTt8sPKdYFwv.PehtSISZx_8QLZnE Passcode Vkf%0@TD * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 29 "P-measures in the random forcing" Damian Sobota (KGRC) Let $\mu$ be a finitely additive probability measure on $\omega$ which vanishes on points, that is, $\mu(\{n\})=0$ for every $n$. It follows immediately that $\mu$ is not $\sigma$-additive, however it may be almost $\sigma$-additive in the following weak sense. We say that $\mu$ is a \textit{P-measure} if for every decreasing sequence $(A_n)$ of subsets of $\omega$ there is a subset $A$ such that $A\setminus A_n$ is finite for every $n$ and $\mu(A)=\lim_n \mu(A_n)$. It follows immediately that, e.g., an ultrafilter $\mathcal{U}$ on $\omega$ is a P-point if and only if the one-point measure $\delta_\mathcal{U}$ is a P-measure. And similarly as in the case of P-points the existence of P-measures is independent of ZFC. During my talk I will discuss basic properties of P-measures and show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic P-measure in the random model. The latter result implies that in this model there exists a nowhere dense ccc P-set in $\omega^*$, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests about the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 31 "Small uncountable objects in Banach space theory" Damian Sobota (KGRC) During my talk I will provide several examples presenting the impact which the (non-)existence of miscellaneous uncountable combinatorial and set-theoretic substructures of various basic spaces (such as the set $P(\mathbb{N})$ of all subsets of the set $\mathbb{N}$ of natural numbers or the set $\mathbb{N}^\mathbb{N}$ of all functions from $\mathbb{N}$ into $\mathbb{N}$) has on structural and topological properties of Banach spaces. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Two seminars March 29: Ibarlucía (10AM) and Neeman (3:30PM)

Carnegie Mellon Logic Seminar
TUESDAY, March 29, 2022 Set Theory Seminar: 10:30 A.M., Online, Tomás Ibarlucía, Université de Paris Please note the unusual time. Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Approximate isomorphism of randomizations with a distinguished small substructure ABSTRACT: I will discuss a joint work with James Hanson in which we study the relation of approximate isomorphism in a certain class of metric structures---specifically, randomizations (in the sense of Ben Yaacov--Keisler) of omega-categorical, omega-stable classical structures, enriched with a predicate for a distinguished small elementary substructure; "small" meaning that the pair consisting of the randomization and its substructure forms a model of the theory of beautiful pairs (in the sense of Poizat) of models of the randomized theory. An approximate isomorphism between two such pairs is an isomorphism of the randomizations that brings the distinguished elementary substructures close in the Hausdorff metric. We prove that for randomized infinite sets with no further structure, any two pairs of this kind are approximately isomorphic (and that this extends to other cases). On the other hand, we show that approximate isomorphism fails for certain pairs of randomized vector spaces over finite sets (and, in fact, for a much larger class of examples). These results provide both a new positive instance and a refutation of a conjecture of Ben Yaacov--Berenstein--Henson, which claimed that if T is an omega-categorical, omega-stable metric theory, then the theory of beautiful pairs of models of T should be approximately omega-categorical. TUESDAY, March 29, 2022 Mathematical logic seminar: 3:30 P.M., Online, Itay Neeman, UCLA Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Restrictions of OCA_T with large continuum ABSTRACT: Todorcevic's Open Coloring Axiom (OCA_T) states that any open graph on a separable metric space is either countably chromatic, or admits an uncountable clique. OCA_T has many interesting and important applications. Its known consistency proofs all lead to models where the continuum is $\aleph_2$. It is therefore natural to ask whether it implies that the continuum is $\aleph_2$, or whether there are other consistency proofs leading to models with larger continuum. (OCA_T negates the CH.) This question is still open. However we show that the restriction of OCA_T to spaces of size less than the continuum is consistent with arbitrarily large values of the continuum. Earlier work by Farah obtained this for the restriction to spaces of size $\aleph_1$

Correction to previous subject line

Carnegie Mellon Logic Seminar
Two seminars March 29: Ibarlucía (10:30AM) and Neeman (3:30PM)

Cross-Alps Logic Seminar (speaker: Omer Ben-Neria)

Cross-Alps Logic Seminar
On Friday 25.03.2022 at 16:00

Omer Ben-Neria (The Hebrew University of Jerusalem)

will give a talk on

Mathias-type Criterion for the Magidor Iteration of Prikry forcings

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.



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Logic Seminar at NUS on Wed 23 March 2022 at 16:00 hrs by Wu Guohua, NTU

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 23 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wu Guohua Title: Splittings and nonsplittings of computably enumerable sets Abstract: In this talk, I will review some existing work on splittings of c.e. sets, and then present an ongoing paper on nonsplitting, a joint work with Downey. The main result is the following. Theorem: There are c.e. sets A and B such that B is strictly Turing reducible to A and for any c.e. sets U, V, if U and V form a set-splitting of A, then one of them is Turing reducible to B. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 21, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 21, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Noson Yanofsky (CUNY)
Title: Why Mathematics Works so Well

Abstract: A major question in philosophy of science involves the unreasonable effectiveness of mathematics in physics. Why should mathematics, created or discovered, with nothing empirical in mind be so perfectly suited to describe the laws of the physical universe? To answer this, we review the well-known fact that the defining properties of the laws of physics are their symmetries. We then show that there are similar symmetries of mathematical facts and that these symmetries are the defining properties of mathematics. By examining the symmetries of physics and mathematics, we show that the effectiveness is actually quite reasonable. In essence, we show that the regularities of physics are a subset of the regularities of mathematics.



- - - - Tuesday, Mar 22, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 22, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Ermek Nurkhaidarov, Penn State Mont Alto
Generic Automorphisms

In this talk we investigate generic automorphisms of countable models. Hodges-Hodkinson-Lascar- Shelah 93 introduces the notion of SI (small index) generic automorphisms which are used to show the small index property. Truss 92 defines the notion of Truss generic automorphisms. We study the relationship between these two types of generic automorphisms.






- - - - Wednesday, Mar 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Joseph Dimos.

Date and Time:     Wednesday March 23, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Introduction to Fusion Categories and Some Applications.


Abstract: Tensor categories and multi-tensor categories have strong alignment with module categories. We can use the multi-tensor categories C in conjunction with classifying tensor algebras wrt C. From here, we can illustrate some examples of tensor categories: the category Vec of k-vector spaces that gives us a fusion category. This is defined as a category Rep(G) of some finite dimensional k-representations of a group G. From here, I will walk through the correspondence of tensor categories (Etingof) and fusion categories. Throughout, I will indicate a few unitary and non-unitary cases of fusion categories. Those unitary fusion categories are those that admit a uniquely monoidal structure. For example, this draws upon [Jones 1983] for finite index and finite depth that bridges a subfactor A-bimodule B to provide a full subcategory of some category A by its module structure. I will discuss some of these components throughout and explain the Morita equivalence of fusion categories.





- - - - Thursday, Mar 24, 2022 - - - -



- - - - Friday, Mar 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna




Next Week in Logic at CUNY:

- - - - Monday, Mar 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dongwoo Kim (CUNY).
Title: Necessity, Essence and Explanation

Abstract: I shall discuss some of the relations between metaphysical modality, essence and explanation. The essentialist approach to metaphysical modality seeks to give an account of necessity (and thus of possibility) as having its source in essence. But what is essence, and in what sense and how does it give rise to necessity? In their recent paper “Essential Properties are Super-Explanatory: Taming Metaphysical Modality” (2020), Marion Godman, Antonella Mallozzi and David Papineau have attempted to address these issues with respect to aposteriori necessities concerning kinds. According to their account, the essence of a kind consists in the super-explanatory property—a single property that is causally responsible for a multitude of commonalities shared by the instances of the kind. And they argue that this super-explanatory notion of essence offers a principled account of aposteriori necessities concerning kinds. In this talk, I am going to argue that their account is not satisfactory. I shall examine two main arguments of GMP that the super-explanatory property of a kind is metaphysically necessary and argue that they both are fallacious. Along the way, a general problem will emerge that applies to any account that tries to explicate the notion of essence in terms of an explanatory relation.





- - - - Tuesday, Mar 29, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Erez Shochat, St. Francis College



- - - - Wednesday, Mar 30, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Morgan Rogers, Universit`a degli Studi dell’Insubria.

Date and Time:     Wednesday March 30, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     TBA.




- - - - Thursday, Mar 31, 2022 - - - -



- - - - Friday, Apr 1, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, April 1, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna






- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

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Kamil Ryduchowski, Elementary submodels and infinitary combinatorics

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 22.03.2022, at 13.15, room 403 Speaker: Kamil Ryduchowski, (MIM UW) Title: Elementary submodels and infinitary combinatorics Abstact: "We will present techniques of using elementary submodels as a tool in infinitary combinatorics. We shall show short, elegant proofs of, among others, the Delta-system lemma, the pressing-down lemma, Erdos-Dushnik-Miller theorem." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) Set Theory Research Seminar talk on Tuesday, March 22

Kurt Godel Research Center
Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 22 "A family of higher dimensional partition principles" Jeffrey Bergfalk (KGRC) This talk will be an exposition of the recent work \emph{A descriptive approach to higher derived limits}, joint with Nathaniel Bannister, Justin Moore, and Stevo Todorcevic (arXiv:2203.00165). The material of this paper is somewhat more ranging than its title would suggest. At its heart is a new family of partition principles which synthesize several recent advances in the study of higher derived limits, rendering those results far more amenable to combinatorial analyses. These principles admit formulation on any directed quasi-order, and are of particular, and interrelated, interest on the quasi-orders $({^\omega}\omega,\leq^*)$ and the ordinals $\omega_n$. A main implication of these principles in any case is the triviality of (higher dimensionally) coherent families of functions; we'll use any remaining time to note ways that such objects, and even higher derived limits, are closer to classical set theoretic concerns than perhaps tends to be realized. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Sam Braunfeld -- Monadic dividing lines and hereditary classes We will discuss how monadic versions of dividing lines in model theory (NIP, stability, NFCP) can be used to prove structure and non-structure results in hereditary classes, which can in turn be used for combinatorial applications. Best, David

Logic seminar Tuesday March 22

Carnegie Mellon Logic Seminar
TUESDAY, March 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Colin Jahel, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Asymptotic theories and homomorphically-avoided structures ABSTRACT: Given a class of finite structures, one can consider μn the uniform measure on structures in said class of size n. We study the asymptotic behavior, when n goes to infinity, of the family (μn)n. In particular, one can ask: which sentences have converging probability, and when is this limit non-zero? I will present our results for classes of graphs and digraphs, in particular classes not containing any homorphic copies of certain sets of finite structures. Joint work with Manuel Bodirsky.

Logic Seminar 16 March 2022 16:00 hrs SGT by Leszek Kolodziejcyk, University of Warsaw

NUS Logic Seminar
Hello, there were various typing errors in the announcement of today's talk including an error of the timing in the email subject. Therefore I resend the announcement. Best regards, Frank Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Yang construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Gruesse aus Singapur

NUS Logic Seminar
Hello, there were various typing errors in the announcement of today's talk including an error of the timing in the email subject. Therefore I resend the announcement. Best regards, Frank Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Yang construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Cross-Alps Logic Seminar (speaker: Damir Dzhafarov)

Cross-Alps Logic Seminar
On Friday 18.03.2022 at 16:00

Damir Dzhafarov (University of Connecticut)

will give a talk on

The SRT22 vs. COH problem

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] itfor the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.



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This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 14, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Wilfrid Hodges (King’s)
Title: Avicenna motivates two new logics

Abstract: The logician Avicenna (Ibn Sina in Arabic) tells us that some thousand and twenty years ago he discovered a group of previously unknown logics. He seems to have been the first logician – at least west of India and after the ancient Greeks – who made any such claim. We will examine two of these new logics and his motivations for them. The first new logic, discovered in around 994 when Avicenna was about eighteen years old, was rediscovered by Boole in the mid 19th century. We will study some features of it that were important to Avicenna (and to some recent logicians) but apparently missed by Boole. The second new logic, probably from around 1000, seems to be the earliest logic with inference rules that act below the surface levels of the formulas. It was impossible to state the inference rules correctly before Frege introduced the notion of scope, but we will see how far Avicenna got.



- - - - Tuesday, Mar 15, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 15, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Thomas Ferguson, University of Amsterdam and University of St. Andrews

Models of Relevant Arithmetic

In the 1970s, the logician and philosopher Robert Meyer proposed a novel response to Goedel's Incompleteness Theorems, suggesting that perhaps the results' impact could be blunted by analyzing Peano arithmetic with a weaker deductive system. Initial successes of the program of relevant arithmetic were positive. E.g., R# (the theory of Peano arithmetic under the relevant logic R) can be shown consistent in the sense of not proving 0=1 and this can be shown through arguably finitistic methods. In this talk I will discuss the rise and fall of Meyer's program, detailing the philosophical foundations, its positive development, and the context of Harvey Friedman's negative result in 1992. I'll also suggest why the program, although not necessarily successful, is nevertheless an interesting object of study.

Also note that a great deal of context—including Meyer's two long-unpublished monographs on the topic—have recently appeared in a special issue of the Australasian Journal of Logic I co-edited with Graham Priest, which can be found at https://ojs.victoria.ac.nz/ajl/issue/view/751.



- - - - Wednesday, Mar 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 16, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).



- - - - Thursday, Mar 17, 2022 - - - -



- - - - Friday, Mar 18, 2022 - - - -


Next Week in Logic at CUNY:

- - - - Monday, Mar 21, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 21, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Noson Yanofsky (CUNY)
Title: Why Mathematics Works so Well

Abstract: A major question in philosophy of science involves the unreasonable effectiveness of mathematics in physics. Why should mathematics, created or discovered, with nothing empirical in mind be so perfectly suited to describe the laws of the physical universe? To answer this, we review the well-known fact that the defining properties of the laws of physics are their symmetries. We then show that there are similar symmetries of mathematical facts and that these symmetries are the defining properties of mathematics. By examining the symmetries of physics and mathematics, we show that the effectiveness is actually quite reasonable. In essence, we show that the regularities of physics are a subset of the regularities of mathematics.



- - - - Tuesday, Mar 22, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 22, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Ermek Nurkhaidarov, Penn State Mont Alto



- - - - Wednesday, Mar 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)

Speaker:     Joseph Dimos.

Date and Time:     Wednesday March 23, 2022, 7:00 - 8:30 PM., on Zoom.

Title:     Introduction to Fusion Categories and Some Applications.


Abstract: Tensor categories and multi-tensor categories have strong alignment with module categories. We can use the multi-tensor categories C in conjunction with classifying tensor algebras wrt C. From here, we can illustrate some examples of tensor categories: the category Vec of k-vector spaces that gives us a fusion category. This is defined as a category Rep(G) of some finite dimensional k-representations of a group G. From here, I will walk through the correspondence of tensor categories (Etingof) and fusion categories. Throughout, I will indicate a few unitary and non-unitary cases of fusion categories. Those unitary fusion categories are those that admit a uniquely monoidal structure. For example, this draws upon [Jones 1983] for finite index and finite depth that bridges a subfactor A-bimodule B to provide a full subcategory of some category A by its module structure. I will discuss some of these components throughout and explain the Morita equivalence of fusion categories.





- - - - Thursday, Mar 24, 2022 - - - -



- - - - Friday, Mar 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Vera Fischer, University of Vienna




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Jakub Andruszkiewicz, The club principle and its connections to the diamond principle

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 15.03.2022, at 13.15, room 403 Speaker: Jakub Andruszkiewicz, (UW/IM PAN) Title: The club principle and its connections to the diamond principle Abstact: The club principle was first introduced by Ostaszewski as a weakening of the diamond principle, as it plays a crucial role in his original construction of the Ostaszewski space. It is well-known that under CH those principles are equivalent and we will present a proof of this fact. We will also show by using an appropriate forcing extension that, as proven by Shelah, assuming CH is essential, i.e. it is consistent relative to ZFC that the club principle holds while the diamond principle does not. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks Tuesday, March 15 and Thursday, March 17

Kurt Godel Research Center
Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 15 "Forcing the \Pi^1_n-uniformization property" Stefan Hoffelner (University of M?nster, Germany) The uniformization property, introduced by N. Lusin in 1930, is an extensively studied notion in descriptive set theory. For a given projective pointclass $\Gamma$ it says that every subset of the plane which belongs to $\Gamma$ has a uniformizing function whose graph is an element of $\Gamma$ as well. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a natural and global description of the behaviour of the uniformization property for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, $\Pi^1_{2n+1}$-sets and hence $\Sigma^1_{2n+2}$-sets do have the uniformization property. Yet the question of universes which display an alternative behaviour of theses regularity properties has remained in large parts a complete mystery, mostly due to the absence of forcing techniques to produce such models. Consequentially, a lot of very natural problems have remained wide open ever since. In my talk, I want to outline some recently obtained tools, which turn the question of forcing a universe with the $\Pi^1_n$-uniformization property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes witness for the first time the consistency (relative to the existence of n-3 many Woodin cardinals) of the $\Pi^1_{n}$-uniformization property, and, for odd n, give new lower bounds in terms of consistency strength. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 17 "Forcing and the Separation, the Reduction and the Uniformization Property" Stefan Hoffelner (University of M?nster, Germany) The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses of the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. These results, impressive as they are, still leave open a lot of natural questions. To name a few we mention: Do we need large cardinals to obtain their effects on the behaviour of these regularity property? Is the $\Sigma^1_{2n+1}$-separation property actually consistent for n >1? More generally: to what extent can we produce set theoretic universes which display a different behaviour of these regularity properties? Are the separation the reduction and the uniformization property different notions at all? The goal of this talk to introduce the three mentioned regularity properties, present a couple of these natural problems and discuss new results, utilising a novel forcing technique, which answer some of them. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- The effect of MA on graphs on omega_1 I'll talk about Todorcevic's result that MA_omega1 implies that every graph on omega_1 without an uncountable independent set contains a clique of ordertype omega^2. Best, David

Logic Seminar 16 March 2022 17:00 hrs at NUS by Leszek Kolodziejczyk

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Young construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Logic Seminar 16 March 2022 17:00 hrs at NUS by Leszek Kolodziejczyk

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Leszek Kolodziejczyk Title: A conservativity result for not-WO(omega^omega) URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The Chong-Slaman-Young construction of a model of RT^2_2 not satisfying Sigma^0_2-induction makes crucial use of a principle known as BME_1. This principle was later shown by Kreuzer and Yokoyama to be equivalent to WO(omega^omega), the statement that omega^omega is well-ordered. I will talk about the following result: if A is any set in a model of RCA_0 + Sigma^0_2-collection such that Sigma_2(A)-induction fails, then there is a descending sequence in omega^omega that is low in A. As a consequence, the negation of WO(omega^omega) is Pi11-conservative over RCA_0 + BSigma^0_2 + not-ISigma^0_2. This result has some potentially interesting corollaries: - If RCA_0 + RT^2_2 is Pi^1_1-conservative over BSigma^0_2, then this can be proved by considering only models in which BME_1 fails. - The formula "X is a well-order" is not provably equivalent to any Sigma^1_1 formula over COH + BSigma^0_2 + not-ISigma^0_2. (In contrast, by earlier work of Fiori Carones, Wong, Yokoyama, and myself, the theory WKL*_0 + not-ISigma^0_1, which is to some extent analogous to COH + BSigma^0_2 + not-ISigma^0_2, proves a collapse of the analytic hierarchy to Delta^1_1.) - There exist two models of RCA_0 + COH + BSigma^0_2 that share a first-order universe and a common counterexample to ISigma^0_2 but are not elementarily equivalent. (In contrast, by the work of Fiori Carones et al. mentioned above, the families of Delta^0_2-definable sets of any such two models have to be elementarily equivalent.) The conservativity result is a side product of a larger project joint with Fiori Carones, Yokoyama, and others.

Cross-Alps Logic Seminar (speaker: Alessandro Andretta)

Cross-Alps Logic Seminar
On Friday 11.03.2022 at 16:00

Alessandro Andretta (University of Turin)

will give a talk on

Sierpinski’s partitions with Sigma^1_2 pieces

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Please write to luca.mottoros [at] unito [dot] it for the link to the event.

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.


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This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 7, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
David Papineau (King’s).
Title: Understanding Causal Inference

Abstract: The current pandemic has focused attention on the techniques used by epidemiologists and other non-experimental scientists to infer causal hypotheses from correlational data. These techniques, which hinge on assumptions about the way causal connections manifest themselves in conditional and unconditional correlations, pose an obvious philosophical challenge. What is it about causation that allows them to work? None of the mainstream accounts of causation—counterfactual, process, dispositional, regularity—casts any light on this question. Probabilistic and interventionist theories of causation do offer a direct response to the challenge, by positing a constitutive connection between causes and correlations, but I shall argue that these theories do not dig deep enough. Instead I shall develop an older idea—which goes back to H.A. Simon in the 1950s—that relates causal relationships to systems of structural equations with probabilistically independent exogenous variables. The attraction of this structural equations approach is that it allows us to view the correlational patterns as fallible evidence for causal relationships, rather than constitutive of them. I shall consider whether this approach can lead to a full reduction of causation and how it might accommodate quantum mechanical unpredictability.





- - - - Tuesday, Mar 8, 2022 - - - -



- - - - Wednesday, Mar 9, 2022 - - - -



- - - - Thursday, Mar 10, 2022 - - - -



- - - - Friday, Mar 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



Logic Workshop
CUNY Graduate Center, Friday, March 11, 2pm
The seminar will take place at the CUNY Graduate Center at 2pm in Room TBA.

Joel David Hamkins, Notre Dame University
Infinite wordle and the mastermind numbers

I shall introduce and consider the natural infinitary variations of Wordle, Absurdle, and Mastermind. Infinite Wordle extends the familiar finite game to infinite words and transfinite play—the code-breaker aims to discover a hidden codeword selected from a dictionary  of infinite words over a countable alphabet  by making a sequence of successive guesswords, receiving feedback after each guess concerning its accuracy. For any dictionary using the usual 26-letter alphabet, for example, the code-breaker can win in at most 26 guesses, and more generally in  guesses for alphabets of finite size . Meanwhile, for some dictionaries on an infinite alphabet, infinite play is required, but the code-breaker can always win by stage  on a countable alphabet, for any fixed dictionary. Infinite Mastermind, in contrast, is a subtler game than Wordle because only the number and not the position of correct bits is given. When duplication of colors is allowed, nevertheless, then the code-breaker can still always win by stage , but in the no-duplication variation, no countable number of guesses (even transfinite) is sufficient for the code-breaker to win. I therefore introduce the mastermind number, denoted , to be the size of the smallest winning no-duplication Mastermind guessing set, a new cardinal characteristic of the continuum, which I prove is bounded below by the additivity number  of the meager ideal and bounded above by the covering number . In particular, the precise value of the mastermind number is independent of ZFC and can consistently be strictly between  and the continuum . In simplified Mastermind, where the feedback given at each stage includes only the numbers of correct and incorrect bits (omitting information about rearrangements), then the corresponding simplified mastermind number is exactly the eventually different number http://jdh.hamkins.org/infinite-wordle-and-the-mastermind-numbers-cuny-logic-workshop-march-2022/




Next Week in Logic at CUNY:

- - - - Monday, Mar 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 14, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Wilfrid Hodges (King’s)
Title: Avicenna motivates two new logics

Abstract: The logician Avicenna (Ibn Sina in Arabic) tells us that some thousand and twenty years ago he discovered a group of previously unknown logics. He seems to have been the first logician – at least west of India and after the ancient Greeks – who made any such claim. We will examine two of these new logics and his motivations for them. The first new logic, discovered in around 994 when Avicenna was about eighteen years old, was rediscovered by Boole in the mid 19th century. We will study some features of it that were important to Avicenna (and to some recent logicians) but apparently missed by Boole. The second new logic, probably from around 1000, seems to be the earliest logic with inference rules that act below the surface levels of the formulas. It was impossible to state the inference rules correctly before Frege introduced the notion of scope, but we will see how far Avicenna got.



- - - - Tuesday, Mar 15, 2022 - - - -

Models of Peano Arithmetic (MOPA)
Monday, March 15, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Models of Relevant Arithmetic
Thomas Ferguson University of Amsterdam and University of St. Andrews



- - - - Wednesday, Mar 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 16, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).



- - - - Thursday, Mar 17, 2022 - - - -



- - - - Friday, Mar 18, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

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CMU math logic seminar on Tuesday, March 15

Carnegie Mellon Logic Seminar
TUESDAY, March 15, 2022 Mathematical logic seminar: 3:30 P.M., Online, Alex Kruckman, Wesleyan University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Properly ergodic structures ABSTRACT: One natural notion of "random (countably infinite) L-structure" is a probability measure on the space of L-structures with domain omega which is invariant and ergodic for the natural action of the symmetric group Sym(omega) on this space. We call such a measure an ergodic structure. The most famous example of an ergodic structure is the Erdős–Rényi random graph model on domain omega, which gives measure 1 to the isomorphism type of the Rado graph. Ergodic structures also arise naturally as limits of sequences of finite structures which are convergent in the appropriate sense, generalizing the graph limits of Lovász and Szegedy. Some ergodic structures (like the Erdős–Rényi random graph model) are almost surely isomorphic to a single countable structure (like the Rado graph), and the countable structures which arise in this way have been completely characterized by Ackerman, Freer, and Patel. In this talk, we will consider properly ergodic structures, those which do not give measure 1 to any single isomorphism type. What do properly ergodic models "look like"? To address this question, we develop an analogue of the Scott rank for ergodic structures, which leads to a precise characterization of those first-order theories (and, more generally, those sentences of the infinitary logic L_{omega_1,omega}) which admit properly ergodic models. This is joint work with Ackerman, Freer, and Patel.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday March 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Higher-dimensional coherent Aronszajn trees We will introduce a family of higher-dimensional analogues of coherent Aronszajn trees arising from a cohomological analysis of ordinals, considered as topological spaces with the order topology. We will investigate the influence of large cardinals on the existence of such higher-dimensional coherent Aronszajn trees and will prove that, if V=L, then these higher-dimensional coherent Aronszajn trees exist everywhere except where ruled out for trivial reasons. We will also present some interesting open questions. This is joint work with Jeffrey Bergfalk. Best, David

(KGRC) seminar talks Tuesday, March 8 and Thursday, March 10

Kurt Godel Research Center
The KGRC welcomes as guests: Jonathan Cancino (host: Vera Fischer) visits the KGRC from March 7 to March 11 and give a talk (see below). Piotr Borodulin-Nadzieja (host: Damian Sobota) visits the KGRC from March 9 to March 13. * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 8 "There may be no I-ultrafilters for any F_\sigma ideal I" Jonathan Cancino (Czech Academy of Sciences, Czech Republic) Given an ideal I and an ultrafilter U, both on \omega, we say that U is an I-ultrafilter if for any f:\omega\to\omega there is A\in U such that f[A]\in I. This notion was introduced by J. Baumgartner in 1995, and it has proved to be very useful in the classification of combinatorial properties of ultrafilters. In particular, the notion of Hausdorff ultrafilter is codify as being G_fc-ultrafilter, where G_fc denotes the ideal of finite chromatic graphs on. We will prove that consistently there is no I-ultrafilter for any F_\sigma ideal I. Since the ideal G_fc is an F_\sigma ideal, our result implies that consistently there is no Hausdorff ultrafilter. This answers a question of M. Di Nasso and M. Forti, among several other questions about the existence of I-ultrafilters. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universit?t Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 1st floor Seminar room 10 Zoom: If you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Thursday, March 10 "The Interplay of Determinacy, Large Cardinals, and Inner Models" Sandra M?ller (TU Wien) The standard axioms of set theory, Zermelo-Fraenkel set theory with Choice (ZFC), do not suffice to answer all questions in mathematics. While this follows abstractly from Kurt G?del's famous incompleteness theorems, we nowadays know numerous concrete examples for such questions. In addition to a large number of problems in set theory, even many problems outside of set theory have been showed to be unsolvable, meaning neither their truth nor their failure can be proven from ZFC. A major part of set theory is devoted to attacking this problem by studying various extensions of ZFC and their properties with the overall goal to identify the "right" axioms for mathematics that settle these problems. Determinacy assumptions are canonical extensions of ZFC that postulate the existence of winning strategies in natural infinite two-player games. Such assumptions are known to enhance sets of real numbers with a great deal of canonical structure. Other natural and well-studied extensions of ZFC are given by the hierarchy of large cardinal axioms. Inner model theory provides canonical models for many large cardinal axioms. Determinacy assumptions, large cardinal axioms, and their consequences are widely used and have many fruitful implications in set theory and even in other areas of mathematics. Many applications, in particular, proofs of consistency strength lower bounds, exploit the interplay of determinacy axioms, large cardinals, and inner models. In this talk I will survey recent developments as well as my contribution to this flourishing area. Time and Place Talk at 3:00pm Universit?t Wien Institut f?r Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien

Cross-Alps Logic Seminar (speaker: Michal Skrzypczak)

Cross-Alps Logic Seminar
Dear all,

On Friday 04.03.2022 at 16:00

Michal Skrzypczak (University of Warsaw)

will give a talk on

The infinite tree - from Kolmogorov, Rabin, and Shelah to modern Theoretical Computer Science

Please refer to the usual webpage of our LogicGroup for more details and the abstract of the talk.

The seminar will be held remotely through Webex. Here are the information to access the meeting:

ACCESS TO WEBEX MEETING

Link Meeting
Number Meeting: 2733 686 2768
Password: ErDGYCdk795

The Cross-Alps Logic Seminar is co-organized by the logic groups of Genoa, Lausanne, Turin and Udine as part of our collaboration in the project PRIN 2017 'Mathematical logic: models, sets, computability'.

All the best,
Luca

--
We sent you this email because you are in the mailing list of Cross-Alps Logic Seminar.
If you do not want to receive our seminar announcements anymore, please write to luca.mottoros@unito.it.

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This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 28, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Michael Burton (Yale).
Title: Paraconsistency with some detachment

Abstract: In this talk, a proof-of-concept logic is presented that is like first-order LP (the “logic of paradox”) except things behave classically within the scope of universal quantifiers. This logic’s material conditional does not, in general, detach, but much can be deduced with it. Structures for this logic are classical first-order structures equipped with a congruence relation, giving this logic a connection to Priest’s collapsing lemma for LP. Some possible improvements to this logic are then discussed. One of these involves separating classicality from universal quantification, having classicality be mediated instead by operators that interact with variable assignments. Finally, the relevance of logics of this kind to various logical paradoxes is discussed.





- - - - Tuesday, Mar 1, 2022 - - - -



- - - - Wednesday, Mar 2, 2022 - - - -



- - - - Thursday, Mar 3, 2022 - - - -



- - - - Friday, Mar 4, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 4, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Tom Benhamou, Tel Aviv University
Subforcings of the Tree-Prikry Forcing

We investigate which forcing notions can be embedded into a Tree-Prikry forcing. It turns out that the answer changes drastically under different large cardinal assumptions. We will focus on the class of strategically closed forcings of cardinality strategically closed forcings of cardinality  and the distributive forcing notions of cardinality . Then we will examine distributive subforcings of the Prikry forcing of cardinality larger than . This is a joint work with Moti Gitik and Yair Hayut.



Next Week in Logic at CUNY:

- - - - Monday, Mar 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, March 7, 4.15-6.15 (NY time), GC 5382
For meeting information (including zoom link for those wishing to attend remotely), please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
David Papineau (King’s).
Title: Understanding Causal Inference

Abstract: The current pandemic has focused attention on the techniques used by epidemiologists and other non-experimental scientists to infer causal hypotheses from correlational data. These techniques, which hinge on assumptions about the way causal connections manifest themselves in conditional and unconditional correlations, pose an obvious philosophical challenge. What is it about causation that allows them to work? None of the mainstream accounts of causation—counterfactual, process, dispositional, regularity—casts any light on this question. Probabilistic and interventionist theories of causation do offer a direct response to the challenge, by positing a constitutive connection between causes and correlations, but I shall argue that these theories do not dig deep enough. Instead I shall develop an older idea—which goes back to H.A. Simon in the 1950s—that relates causal relationships to systems of structural equations with probabilistically independent exogenous variables. The attraction of this structural equations approach is that it allows us to view the correlational patterns as fallible evidence for causal relationships, rather than constitutive of them. I shall consider whether this approach can lead to a full reduction of causation and how it might accommodate quantum mechanical unpredictability.





- - - - Tuesday, Mar 8, 2022 - - - -



- - - - Wednesday, Mar 9, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Jin-Cheng Guu, Stony Brook University.
Date and Time:     Wednesday March 9, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Topological Quantum Field Theories from Monoidal Categories.

Abstract: We will introduce the notion of a topological quantum field theory (tqft) and a monoidal category. We will then construct a few (extended) tqfts from monoidal categories, and show how quantum invariants of knots and 3-manifolds were obtained. If time permits, I will discuss (higher) values in (higher) codimensions based on my recent work on categorical center of higher genera (joint with A. Kirillov and Y. H. Tham).





- - - - Thursday, Mar 10, 2022 - - - -



- - - - Friday, Mar 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
William Chan, Carnegie Mellon University



Logic Workshop
CUNY Graduate Center, Friday, March 11, 2pm
The seminar will take place at the CUNY Graduate Center at 2pm in Room TBA.

Joel David Hamkins, Notre Dame University
Infinite wordle and the mastermind numbers

I shall introduce and consider the natural infinitary variations of Wordle, Absurdle, and Mastermind. Infinite Wordle extends the familiar finite game to infinite words and transfinite play—the code-breaker aims to discover a hidden codeword selected from a dictionary  of infinite words over a countable alphabet  by making a sequence of successive guesswords, receiving feedback after each guess concerning its accuracy. For any dictionary using the usual 26-letter alphabet, for example, the code-breaker can win in at most 26 guesses, and more generally in  guesses for alphabets of finite size . Meanwhile, for some dictionaries on an infinite alphabet, infinite play is required, but the code-breaker can always win by stage  on a countable alphabet, for any fixed dictionary. Infinite Mastermind, in contrast, is a subtler game than Wordle because only the number and not the position of correct bits is given. When duplication of colors is allowed, nevertheless, then the code-breaker can still always win by stage , but in the no-duplication variation, no countable number of guesses (even transfinite) is sufficient for the code-breaker to win. I therefore introduce the mastermind number, denoted , to be the size of the smallest winning no-duplication Mastermind guessing set, a new cardinal characteristic of the continuum, which I prove is bounded below by the additivity number  of the meager ideal and bounded above by the covering number . In particular, the precise value of the mastermind number is independent of ZFC and can consistently be strictly between  and the continuum . In simplified Mastermind, where the feedback given at each stage includes only the numbers of correct and incorrect bits (omitting information about rearrangements), then the corresponding simplified mastermind number is exactly the eventually different number http://jdh.hamkins.org/infinite-wordle-and-the-mastermind-numbers-cuny-logic-workshop-march-2022/





- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 2nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Noé de Rancourt -- On countable unions of Borel equivalence relations I'll talk about dichotomies of Borel equivalence relations obtained with Benjamin Miller which characterize the obstructions for an equivalence relation to be in a given complexity class F assuming we know it is a countable union of relations from F. Our simplest result is in some sense an extension of Kechris-Louveau's E_1-dichotomy. There will be no proofs, because those are way too long. Best, David

European Set Theory Conference: 29 August - 2 September 2022

Conference
EUROPEAN SET THEORY CONFERENCE 2022 August 29th-September 2nd, 2022 Turin, Italy We are pleased to announce that the registration for the ESTC2022 is now open! (See below for the relevant deadlines.) Various forms of financial support for young researchers are available. It is also possible to submit a title and abstract for a contributed talk; submissions will be evaluated by the Scientific Committee, and a decision will be communicated 2-3 months before the conference. Please visit our website or contact us through this form for more information. The conference will be held in person, we are confident that at the end of the summer the pandemic situation will be under control. It will be nice to meet in person again, after these challenging years. Also, it is a very good season to visit Turin, a beautiful city in northern Italy, while attending one of the most exciting conferences in set theory! If you are interested, please register as soon as possible, and do not forget to submit your title and abstract if you want to contribute with a short talk. We also kindly ask you to share this announcement with all people who might be interested in the event. IMPORTANT DEADLINES: 30/04/2022: Abstract submission for contributed talks 30/06/2022: Early registration with reduced fee 22/08/2022: Registration MORE ON THE CONFERENCE: The European Set Theory Conferences is a series of biannual meetings coordinated by the European Set Theory Society (ESTS). This year's edition is organized by the Department of Mathematics of the University of Turin and ESTS, in partnership with the Clay Mathematics Institute. It is the most important conference in set theory, and gathers the worldwide leaders in the field as well as many young researchers. During the event, the prestigious Hausdorff medal will be awarded for the most influential work in set theory published in the preceding five years. There will also be a special session in honor of Boban Veličković's 60th birthday. Invited speakers - Jeffrey Bergfalk (Vienna) - Filippo Calderoni (Chicago) - Natasha Dobrinen (Denver) - Osvaldo Guzmán (Mexico) - Joel Hamkins (Notre Dame) - Chris Lambie-Hanson (Prague) - Martino Lupini (New Zealand) - Julien Melleray (Lyon) - Andrew Marks (UCLA) - Sandra Müller (Vienna) - Saharon Shelah (Jerusalem) - Stevo Todorčević (Toronto and Paris) - Jouko Väänänen (Helsinki) - Zoltán Vidnyánsky (Caltech) - Trevor Wilson (Miami) Tutorials - Yair Hayut (Jerusalem) - Grigor Sargsyan (Poland) Boban Veličković's 60th Birthday Celebration - Laura Fontanella (Paris) - Rahman Mohammadpour (Vienna) - Giorgio Venturi (Brasil) - Matteo Viale (Turin) Scientific committee Joan Bagaria (chair), Matthew Foreman, Moti Gitik, Péter Komjáth, Piotr Koszmider, Heike Mildenberger, Luca Motto Ros, John Steel Local organizing committee Alessandro Andretta, Raphaël Carroy, Luca Motto Ros, Gianluca Paolini, Francesco Parente, Salvatore Scamperti, Matteo Viale
Link to more info

Logic Seminar Wed 2 March 2022 16:00 hrs at NUS by Lavinia Picollo

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 2 March 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Lavinia Picollo, NUS Title: High-order logic and disquotational truth URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Truth predicates are widely believed to be capable of serving a certain logical or quasi-logical function. There is little consensus, however, on the exact nature of this function. We offer a series of formal results in support of the thesis that disquotational truth is a device to simulate higher-order resources in a first-order setting. More specifically, we show that any theory formulated in a higher-order language can be naturally and conservatively interpreted in a first-order theory with a disquotational truth or truth-of predicate. In the first part of the talk we focus on the relation between truth and full impredicative sentential quantification. The second part is devoted to the relation between truth-of and full impredicative predicate quantification. This is joint work with Thomas Schindler

(KGRC) Set Theory Seminar talk on Tuesday, March 1

Kurt Godel Research Center
The KGRC welcomes as guests: Sarka Stejskalova and Radek Honzik (host: Sy-David Friedman) visit the KGRC until February 28. * * * Set Theory Research Seminar Kurt G?del Research Center Tuesday, March 1 "Ramsey Theory of Ordinals and Finite Combinatorics" Thilo Weinert (KGRC) The Ramsey Theory of Ordinals has been investigated over the last decades and a large variety of results have been attained. The talk is going to focus on the Ramsey Theory of finite multiples both of infinite cardinals and, in some cases products of two infinite cardinals. This leads to problems in finite combinatorics similar to the calculation of finite Ramsey numbers. On the one hand, exact results are usually only obtainable if the natural numbers involved remain somewhat small. On the other hand, sometimes asymptotic results can be attained. More concretely, for any ordinal $\alpha$ and $\beta$, let $r(\alpha, \beta)$ denote the least ordinal $\gamma$ such that any colouring of the pairs in $\gamma$ in black and white either allows for a homogeneously white subset of order-type $\alpha$ or a homogeneously black subset of order-type $\beta$. Since the nineties it is known that the growth of $r(n, 3)$ is of order $n^2/log(n)$. It turns out that for any infinite cardinal $\lambda$, we have $r(\lambda * n, 3) = \lambda * r(I_n, L_3)$ where the growth of $r(I_n, L_3)$ is of order $n^2/log(n)$ as well. Similarly, if $\kappa > \lambda$ is weakly compact, we have $r(\kappa * \lambda * n, 3) = \kappa * \lambda * r(I_n, S_3) where, again, the growth of $r(I_n, L_3)$ is of order $n^2/log(n)$. Finally there is a finitary characterisation of the Ramsey numbers $r(\omega^2 *n, k)$ for natural numbers $n$ and $k$. However the growth behaviour of $r(\omega^2 * n, 3)$ is still unknown. This is partly joint work with Ferdinand Ihringer and Deepak Rajendraprasad. Time and Place Talk at 3:00pm in hybrid mode, in person as well as via Zoom. Universitt Wien Institut f?r Mathematik Kolingasse 14-16 1090 Wien 2nd floor Seminar room 10 Talk at 3:00pm -- if you need the Zoom data and have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) Students at Uni Wien are strongly encouraged to attend the seminar in person. * * * Logic Colloquium Kurt G?del Research Center Please note that Sandra M?llers talk had to be rescheduled to March 10.

Two CMU seminars next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, March 1, 2022 Mathematical logic seminar: 3:30 P.M., Online, Aristotelis Panagiotopoulos, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Every CBER is smooth below a Milliken-generic strong subtree (Part I) ABSTRACT: The theory of Borel reductions becomes a very delicate subject of study when one restricts attention to the class of Countable Borel Equivalence Relations (CBERs). Indeed, no matter how complex a CBER is, its complexity tends to reside on a "small" piece of its domain. For example a result of Hjorth and Kechris states that every CBER on a Polish space is hyperfinite when restricted to some comeager set. Similarly, classical results of Mathias about forcing extensions by Mathias reals imply that every CBER on the Ellentuck Ramsey space is hyperfinite when restricted to some pure Ellentuck cube. In this talk we show that the Milliken space M of strong trees satisfies a much stronger canonization property: if E is CBER on M then for the Milliken-generic T in M we have that E and = agree on the pure Milliken cube [T]. This is joint work with Allison Wang. TUESDAY, March 1, 2022 Set theory reading group: 4:30 P.M., Online, Allison Wang, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: Every CBER is smooth below a Milliken-generic strong subtree (Part II) ABSTRACT: The theory of Borel reductions becomes a very delicate subject of study when one restricts attention to the class of Countable Borel Equivalence Relations (CBERs). Indeed, no matter how complex a CBER is, its complexity tends to reside on a "small" piece of its domain. For example a result of Hjorth and Kechris states that every CBER on a Polish space is hyperfinite when restricted to some comeager set. Similarly, classical results of Mathias about forcing extensions by Mathias reals imply that every CBER on the Ellentuck Ramsey space is hyperfinite when restricted to some pure Ellentuck cube. In this talk we show that the Milliken space M of strong trees satisfies a much stronger canonization property: if E is CBER on M then for the Milliken-generic T in M we have that E and = agree on the pure Milliken cube [T]. This is joint work with Aristotelis Panagiotopoulos.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 21, 2022 - - - -



- - - - Tuesday, Feb 22, 2022 - - - -



- - - - Wednesday, Feb 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     David Roberts.
Date and Time:     Wednesday February 23, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Do you have what it takes to use the diagonal argument?

Abstract: Lawvere's reformulation of the diagonal argument captured many instances from the literature in an elegant and abstract category-theoretic treatment. The original version used cartesian closed categories, but gave a nod to how the statement of the argument could be adjusted so as to make fewer demands on the category. In fact the argument, and the fixed-point theorem that Lawvere provided as the positive version of the argument, both require much less than Lawvere stated. This talk will give an outline of Lawvere's version of the diagonal argument, his corresponding fixed-point theorem, and then cover a few versions obtained recently that drop assumptions on the properties/structure of the category at hand.





- - - - Thursday, Feb 24, 2022 - - - -



- - - - Friday, Feb 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Richard Matthews, University of Leeds
Big classes and the respected model

In standard (ZFC) set theory, proper classes are not sets because they are too 'big' or, to put it in a formal way, because they surject onto any non-zero ordinal. We shall study this notion of 'bigness' in weaker systems of set theory, in particular those in which the Power Set Axiom fails. We will observe that in many such theories it is possible to have proper classes which are not big.

As part of this, we shall see a failed attempt to find a proper class which is not big in the theory ZF without Power Set but with Collection - which is by taking a certain symmetric submodel of a class forcing. It will turn out that this approach fails because, unlike in the set forcing case, the symmetric submodel of a class forcing need not exhibit many of the nice properties that we would expect. Notably, Collection may fail and, in fact, it is unclear which axioms need necessarily hold.

This will lead to the definition of the 'Respected Model', an alternative approach to defining a submodel of a class forcing in which Choice fails. We will investigate the properties of this new model and compare it to the symmetric version.





- - - - Monday, Feb 28, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 28, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Michael Burton (Yale).
Title: Paraconsistency with some detachment

Abstract: In this talk, a proof-of-concept logic is presented that is like first-order LP (the “logic of paradox”) except things behave classically within the scope of universal quantifiers. This logic’s material conditional does not, in general, detach, but much can be deduced with it. Structures for this logic are classical first-order structures equipped with a congruence relation, giving this logic a connection to Priest’s collapsing lemma for LP. Some possible improvements to this logic are then discussed. One of these involves separating classicality from universal quantification, having classicality be mediated instead by operators that interact with variable assignments. Finally, the relevance of logics of this kind to various logical paradoxes is discussed.





- - - - Tuesday, Mar 1, 2022 - - - -



- - - - Wednesday, Mar 2, 2022 - - - -



- - - - Thursday, Mar 3, 2022 - - - -



- - - - Friday, Mar 4, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, March 4, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Tom Benhamou, Tel Aviv University


- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Next CMU math logic seminar

Carnegie Mellon Logic Seminar
TUESDAY, February 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Sam Sanders, Ruhr-Universitaet Bochum Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The two-dimensional nature of ordinary mathematics ABSTRACT: The usual foundations of mathematics (ZFC set theory) are 'two-dimensional' in nature in that given a theorem T provable in ZFC, the following two questions are unavoidable: a) is T provable in ZF alone? b) If not, which fragment of the Axiom of Choice (AC) does T imply? One reason to make this distinction is that the choice functions from AC are fundamentally non-constructive in nature (even relative to ZF). We show that ordinary mathematics, when formulated in the language of third-order arithmetic, is similarly two-dimensional in nature in that the following questions are fundamental for a theorem S: c) Is S provable from (conventional) comprehension alone? d) If not, which fragment of the neighborhood function principle (NFP) does S imply? Intellectually pleasing, NFP is a fragment of AC with continuous choice functions, i.e. provable in ZF (and much weaker systems). We discuss the weakest principle falling under d), namely the uncountability of R, and how NFP gives rise to a new computational model for comparing theorems of ordinary mathematics. This is joint work with Dag Normann.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 23rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindrich Zapletal -- Geometric set theory II This is a continuation from the previous week. I will prove a couple of basic feature of balanced extensions of the Solovay model: they add no new sets of ordinals and contain no MAD families in particular. I will also produce the first example of a consistency result: it is consistent with ZF+DC to have a Hamel basis for R over Q, but no nonprincipal ultrafilter on natural numbers. Best, David

Logic Seminar today at 16:30 hrs

NUS Logic Seminar
Hello, a short reminder that the logic seminar today starts at 16:30 hrs Singapore time, not at the full hour as usual. Regards, Frank

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 16th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jindřich Zapletal -- Geometric Set Theory I will explain basics of the method developed with Paul Larson which obtains consistency results in choiceless set theory ZF+DC using definable forcing extensions of the Solovay model. Among recent applications, if n>0 is a natural number and Gn is the graph on n-dimensional Euclidean space connecting points of rational distance, it is consistent with ZF+DC that Gn has countable chromatic number while Gn+1 does not. Best, David

Logic Seminar Wed 16 February 2022 16:30 hrs by Rupert Hoelzl

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 February 2022, 16:30 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl, Universitaet der Bundeswehr, Muenchen Title: Universality, optimality and randomness deficiency URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: A Martin-Loef test U is universal if it captures all sequences which are not Martin-Loef random. It is optimal if for every Martin-Loef test V there is a constant c such that, for all n, V_{n+c} subseteq U_n. We study the computational differences between universal and optimal Martin-Loef tests as well as the effects of these differences on both the notions of layerwise computability and the Weihrauch degree of LAY, the function that produces a bound on the randomness deficiency of a given Martin-Loef random sequence. We prove several robustness and idempotence results concerning the Weihrauch degree of LAY and we show that layerwise computability is more restrictive than Weihrauch reducibility to LAY. Along similar lines, we also study the principle RD, a variant of LAY outputting the precise randomness deficiency of sequences instead of only an upper bound as LAY. This is joint work with Paul Shafer. The paper is available as in the Annals of Pure and Applied Logic, https://doi.org/10.1016/j.apal.2015.05.006

Logic Seminar Wed 16 February 2022 16:30 hrs by Rupert Hoelzl

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 16 February 2022, 16:30 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl, Universitaet der Bundeswehr, Muenchen Title: Universality, optimality and randomness deficiency URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: A Martin-Loef test U is universal if it captures all sequences which are not Martin-Loef random. It is optimal if for every Martin-Loef test V there is a constant c such that, for all n, V_{n+c} subseteq U_n. We study the computational differences between universal and optimal Martin-Loef tests as well as the effects of these differences on both the notions of layerwise computability and the Weihrauch degree of LAY, the function that produces a bound on the randomness deficiency of a given Martin-Loef random sequence. We prove several robustness and idempotence results concerning the Weihrauch degree of LAY and we show that layerwise computability is more restrictive than Weihrauch reducibility to LAY. Along similar lines, we also study the principle RD, a variant of LAY outputting the precise randomness deficiency of sequences instead of only an upper bound as LAY. This is joint work with Paul Shafer. The paper is available as in the Annals of Pure and Applied Logic, https://doi.org/10.1016/j.apal.2015.05.006

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 14, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Ekaterina Kubyshkina (Campinas)
Title: Ignorance as an excuse, formally

Abstract: In the current literature on epistemology there is a lively debate on which type of ignorance may provide a moral excuse. A good candidate is the one in which an agent has never considered or thought about a true proposition p. From a logical perspective, it is usual to model situations involving ignorance by means of epistemic logic. However, no formal analysis was provided for ignorance as an excuse. First, we will argue that if ignorance is expressed via standard modalities of knowledge and belief, one is unable to represent ignorance as an excuse. Secondly, we fill this gap by providing an original logical setting for modelling this type of ignorance. In particular, we introduce a complete and sound logic in which ignorance is expressed as a primitive modality. Semantically, the logic is characterized by Kripke semantics with possibly incomplete worlds. Moreover, in order to consider the conditions of a possible change of an agent’s ignorance, we will extend the setting by considering public announcements.



- - - - Tuesday, Feb 15, 2022 - - - -



- - - - Wednesday, Feb 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Date and Time:     Wednesday February 16, 2022, 7:00 - 8:30 PM., IN PERSON MEETING, GC Room 6417.
Speaker:     Emilio Minichiello, CUNY Graduate Center.
Title:     Category Theory ∩ Differential Geometry.

·  Abstract: In this talk we will take a tour through some areas of math at the intersection of category theory and differential geometry. We will talk about how the use of category theory works towards solving 2 problems: 1) to give rigorous definitions and techniques to study increasingly complicated objects in differential geometry that are coming from physics, like orbifolds and bundle gerbes, and 2) to find good categories in which to embed the category of finite dimensional smooth manifolds, without losing too much geometric intuition. This involves the study of Lie groupoids, sheaves, diffeological spaces, stacks, and infinity stacks. I will try to motivate the use of these mathematical objects and how they help mathematicians understand differential geometry and expand its scope.


- - - - Thursday, Feb 17, 2022 - - - -



- - - - Friday, Feb 18, 2022 - - - -


Set Theory Seminar
CUNY Graduate Center, Friday, February 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders: Part II

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.






Next Week in Logic at CUNY:

- - - - Monday, Feb 21, 2022 - - - -



- - - - Tuesday, Feb 22, 2022 - - - -



- - - - Wednesday, Feb 23, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     David Roberts.
Date and Time:     Wednesday February 23, 2022, 7:00 - 8:30 PM., on Zoom.
Title:     Do you have what it takes to use the diagonal argument?

Abstract: Lawvere's reformulation of the diagonal argument captured many instances from the literature in an elegant and abstract category-theoretic treatment. The original version used cartesian closed categories, but gave a nod to how the statement of the argument could be adjusted so as to make fewer demands on the category. In fact the argument, and the fixed-point theorem that Lawvere provided as the positive version of the argument, both require much less than Lawvere stated. This talk will give an outline of Lawvere's version of the diagonal argument, his corresponding fixed-point theorem, and then cover a few versions obtained recently that drop assumptions on the properties/structure of the category at hand.





- - - - Thursday, Feb 24, 2022 - - - -



- - - - Friday, Feb 25, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 25, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Richard Matthews, University of Leeds




- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Next two CMU math logic seminars

Carnegie Mellon Logic Seminar
TUESDAY, February 15, 2022 Mathematical logic seminar: 3:30 P.M., Online, Dag Normann, University of Oslo Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The complexity of operators constructed in mainstream mathematics ABSTRACT: In an ongoing project with Sam Sanders, we have analysed third order theorems in mainstream mathematics both from the viewpoints of Kohlenbach's higher order reverse mathematics and Kleene's higher order computability theory. Based on case studies involving theorems like the Heine-Borel theorem, Lindelöf's lemma and the Jordan decomposition theorem we observe that constructions in mainstream mathematics give rise to natural functionals of type three of a kind that hitherto has remained unobserved in higher order computability theory. In this talk we will discuss both such case studies and a possible complexity/computability model useful for discussing the nature of such operators. TUESDAY, February 22, 2022 Mathematical logic seminar: 3:30 P.M., Online, Sam Sanders, Ruhr-Universitaet Bochum Join Zoom Meeting: https://cmu.zoom.us/j/92655324096?pwd=VUhSSlkrdHMxbTlSYUMxYzFXM01kdz09 Meeting ID: 926 5532 4096 Passcode: 555455 TITLE: The two-dimensional nature of ordinary mathematics ABSTRACT: The usual foundations of mathematics (ZFC set theory) are 'two-dimensional' in nature in that given a theorem T provable in ZFC, the following two questions are unavoidable: a) is T provable in ZF alone? b) If not, which fragment of the Axiom of Choice (AC) does T imply? One reason to make this distinction is that the choice functions from AC are fundamentally non-constructive in nature (even relative to ZF). We show that ordinary mathematics, when formulated in the language of third-order arithmetic, is similarly two-dimensional in nature in that the following questions are fundamental for a theorem S: c) Is S provable from (conventional) comprehension alone? d) If not, which fragment of the neighborhood function principle (NFP) does S imply? Intellectually pleasing, NFP is a fragment of AC with continuous choice functions, i.e. provable in ZF (and much weaker systems). We discuss the weakest principle falling under d), namely the uncountability of R, and how NFP gives rise to a new computational model for comparing theorems of ordinary mathematics. This is joint work with Dag Normann.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 7, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Guillermo Badia (Queensland)
Title: Frame Definability in Finitely-Valued Modal Logics

Abstract: In this paper we study frame definability in finitely-valued modal logics and establish two main results via suitable translations: (1) in finitely-valued modal logics one cannot define more classes of frames than are already definable in classical modal logic, and (2) a large family of finitely-valued modal logics define exactly the same classes of frames as classical modal logic (including modal logics based on finite Heyting and MV-algebras). In this way one may observe, for example, that the celebrated Goldblatt–Thomason theorem applies immediately to these logics. In particular, we obtain the central result from [B. Teheux. Modal definability for Łukasiewicz validity relations. Studia Logica 104 (2): 343–363 (2016)] with a much simpler proof and answer one of the open questions left in that paper. Moreover, the proposed translations allow us to determine the computational complexity of a big class of finitely-valued modal logics.

Note: This is joint work with Carles Noguera and Xavier Caicedo.



- - - - Tuesday, Feb 8, 2022 - - - -



- - - - Wednesday, Feb 9, 2022 - - - -



- - - - Thursday, Feb 10, 2022 - - - -



- - - - Friday, Feb 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 11, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.




Next Week in Logic at CUNY:

- - - - Monday, Feb 14, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 14, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Ekaterina Kubyshkina (Campinas)
Title: Ignorance as an excuse, formally

Abstract: In the current literature on epistemology there is a lively debate on which type of ignorance may provide a moral excuse. A good candidate is the one in which an agent has never considered or thought about a true proposition p. From a logical perspective, it is usual to model situations involving ignorance by means of epistemic logic. However, no formal analysis was provided for ignorance as an excuse. First, we will argue that if ignorance is expressed via standard modalities of knowledge and belief, one is unable to represent ignorance as an excuse. Secondly, we fill this gap by providing an original logical setting for modelling this type of ignorance. In particular, we introduce a complete and sound logic in which ignorance is expressed as a primitive modality. Semantically, the logic is characterized by Kripke semantics with possibly incomplete worlds. Moreover, in order to consider the conditions of a possible change of an agent’s ignorance, we will extend the setting by considering public announcements.



- - - - Tuesday, Feb 15, 2022 - - - -



- - - - Wednesday, Feb 16, 2022 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Date and Time:     Wednesday February 16, 2022, 7:00 - 8:30 PM., IN PERSON MEETING, GC Room 6417.
Speaker:     Emilio Minichiello, CUNY Graduate Center.
Title:     Category Theory ∩ Differential Geometry.

·  Abstract: In this talk we will take a tour through some areas of math at the intersection of category theory and differential geometry. We will talk about how the use of category theory works towards solving 2 problems: 1) to give rigorous definitions and techniques to study increasingly complicated objects in differential geometry that are coming from physics, like orbifolds and bundle gerbes, and 2) to find good categories in which to embed the category of finite dimensional smooth manifolds, without losing too much geometric intuition. This involves the study of Lie groupoids, sheaves, diffeological spaces, stacks, and infinity stacks. I will try to motivate the use of these mathematical objects and how they help mathematicians understand differential geometry and expand its scope.


- - - - Thursday, Feb 17, 2022 - - - -



- - - - Friday, Feb 18, 2022 - - - -


Set Theory Seminar
CUNY Graduate Center, Friday, February 18, 12:30pm
The seminar will take place virtually at 12:30pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders: Part II

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Logic Seminar Wed 9 Feb 2022 16:00 hrs at NUS by Xie Ruofei

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 9 February 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Xie Ruofei Title: Convergence property and randomness URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Consider the sum of the series (-1)^{x_n}a_n over n, where x_n is a binary sequence and a_n is a sequence of real numbers. We say the sequence x_n has convergence property if the sum above converges for every computable sequence of real numbers whose sum \sum_n a_n^2 converges computably. Downey, Greenberg, and Tanggara showed in their unpublished paper that every Schnorr random series x_n has convergence property. In this talk, we will focus on convergence property and show its similarities and differences with randomness. This is joint work with Noam Greenberg.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday February 9th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino -- There may be no I-ultrafilter for any F_sigma ideal I (continued) The notion of I-ultrafilter was introduced by Baumgartner, and it has been useful in providing a framework for classifying many combinatorial properties of ultrafilters. In this talk we prove, however, that the class of F_sigma ideals may provide a vacuous classification of the combinatorial properties of ultrafilters, that is, F_sigma ideals may be not useful in providing combinatorial information about ultrafilters. This in turn implies that consistently there is no Hausdorff ultrafilter, thus answering a classical question of M. Di Nasso and M. Forti. Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
Welcome back, everyone!
- Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 31, 2022 - - - -



- - - - Tuesday, Feb 1, 2022 - - - -



- - - - Wednesday, Feb 02, 2022 - - - -



- - - - Thursday, Feb 03, 2022 - - - -



- - - - Friday, Feb 04, 2022 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Feb 7, 2022 - - - -

Logic and Metaphysics Workshop
Date: Monday, February 7, 4.15-6.15 (NY time), GC 5382
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Guillermo Badia (Queensland)
Title: Frame Definability in Finitely-Valued Modal Logics

Abstract: In this paper we study frame definability in finitely-valued modal logics and establish two main results via suitable translations: (1) in finitely-valued modal logics one cannot define more classes of frames than are already definable in classical modal logic, and (2) a large family of finitely-valued modal logics define exactly the same classes of frames as classical modal logic (including modal logics based on finite Heyting and MV-algebras). In this way one may observe, for example, that the celebrated Goldblatt–Thomason theorem applies immediately to these logics. In particular, we obtain the central result from [B. Teheux. Modal definability for Łukasiewicz validity relations. Studia Logica 104 (2): 343–363 (2016)] with a much simpler proof and answer one of the open questions left in that paper. Moreover, the proposed translations allow us to determine the computational complexity of a big class of finitely-valued modal logics.

Note: This is joint work with Carles Noguera and Xavier Caicedo.



- - - - Tuesday, Feb 8, 2022 - - - -



- - - - Wednesday, Feb 9, 2022 - - - -



- - - - Thursday, Feb 10, 2022 - - - -



- - - - Friday, Feb 11, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center, Friday, February 11, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sittinon Jirattikansakul, Tel Aviv University
Forcing with overlapping supercompact extenders

In the paper 'Blowing up the power of a singular cardinal of uncountable cofinality', Gitik introduced the forcing which can violate the SCH at singular cardinals of any cofinalities, assuming that the singular cardinals are also singular in the ground model. The forcing is built up from a Mitchell increasing sequence of strong extenders, and it preserves all cardinals and cofinalities in the generic extension. In this talk, we will discuss a forcing which is built from a Mitchell increasing sequence of supercompact extenders. The forcing also violates the SCH at singular cardinals of any cofinalities which are singular in the ground model. An important feature of this forcing is that it is possible to collapse the successor of a singular cardinal, while preserving cardinals above it.



- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Logic Seminar 3 February 2022 16:00 hrs at NUS by Andre Nies

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Thursday, 3 February 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Andre Nies, The University of Auckland Title: The structure of the class of K-trivial sets URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The K-trivial sets are antirandom in the sense that the initial segment complexity in terms of prefix-free Kolmogorov complexity K grows as slowly as possible. Chaitin introduced this notion in about 1975, and showed that each K-trivial is Turing below the halting set. Shortly after, Solovay proved that a K-trivial set can be noncomputable. In the past two decades, many alternative characterisations of this class have been found: properties such as being low for K, low for Martin-Loef (ML) randomness, and a basis for ML randomness, which state in one way or the other that the set is close to computable. Initially, the class of noncomputable K-trivials appeared to be amorphous. More recently, an internal structure has been found. Most of these results can be phrased in the language of a reducibility on the K-trivials which is weaker than Turing's: A is ML-below B if each ML-random computing B also computes A. Bienvenu, Greenberg, Kucera, Nies and Turetsky (JEMS 2016) showed that there an ML complete K-trivial set. Greenberg, Miller and Nies (JML, 2019) established a dense hierarchy of subclasses of the K-trivials based on fragments of Omega computing the set, and each such subclass is an initial segment for ML. More recent results (see arxiv.org/abs/1707.00258, updated and submitted Dec 2020) generalise these approaches using cost functions. They also show that each K-trivial set is ML-equivalent to a c.e. K-trivial. The extreme lowness of K-trivials, far from being an obstacle, allows for methods which don't work in a wider setting. The talk provides an overview and discusses open questions. For instance, is ML-completeness an arithmetical property of K-trivials? This is joint work with Noam Greenberg, Joseph Miller and Dan Turetsky

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Rupert McCallum
TITLE: Intrinsic Justifications in Set theory
DATE: 2 February 2022
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Logic Seminar 26 January 2022 16:00 hrs at NUS by Zhang Jing (today)

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 26 January 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Zhang Jing Title: Ramsey-type theorems on large structures URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Structures like trees, linear orders, partial orders, graphs have been widely studied in different areas of mathematics. The Ramsey-type theorems we will discuss usually take the following form: for any given coloring of the structure, there exists a "large sub-structure" that intersects "very few" color classes. One example is a theorem of Laver that states for any finite coloring of Q x Q (ordered pairs of rationals), there exists X, Y order isomorphic to Q, such that X x Y intersects at most 2 color classes. We will discuss the uncountable analogues of these statements and their consistency. In particular, a diagonal version of the Halpern-Lauchli theorem plays a key role. The differences between countable combinatorics and uncountable combinatorics will be highlighted.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 26th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Jonathan Cancino -- There may be no I-ultrafilter for any F_sigma ideal I The notion of I-ultrafilter was introduced by Baumgartner, and it has been useful in providing a framework for classifying many combinatorial properties of ultrafilters. In this talk we prove, however, that the class of F_sigma ideals may provide a vacuous classification of the combinatorial properties of ultrafilters, that is, F_sigma ideals may be not useful in providing combinatorial information about ultrafilters. This in turn implies that consistently there is no Hausdorff ultrafilter, thus answering a classical question of M. Di Nasso and M. Forti. Best, David

(KGRC) video recording of Víctor Torres's talk

Kurt Godel Research Center
A recording of the talk of Víctor Torres from January 13th at the KGRC Logic Colloquium can be found here: https://univienna.zoom.us/rec/share/c3uO9AKcscJmC_PiuEwwdF_keDWgnGJaXjHykFSUX3pvdT5huEU0BHjw5rFdJdVc.AN_ekNznONDnOZD0 Password: !F8^vg followed by 7j

(KGRC) Logic Colloquium talk on Thursday, January 27

Kurt Godel Research Center
Logic Colloquium Kurt Gödel Research Center Thursday, January 27 "The Banach-Tarski paradox, monsters and their gentler cousins" Yash Lodha (Uni Wien) The Banach-Tarski paradox is one of the most striking and counterintuitive phenomena in all of mathematics. Von Neumann's study of the paradox led to the formulation of the so called von Neumann-Day problem, which has been attributed to Mahlon Day from the 1950s. The problem was solved in the late 70s by the construction of various finitely generated "monster" groups. However, I will explain how elementary tools from descriptive set theory recently led to the construction of considerably "less scary" new solutions, some of which are finitely presented (and even type F_{\infty}). Time and Place Talk at 3:00pm via Zoom--if you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Welcome back, and Happy New Year!  Note that CUNY's semester begins on January 28th.  However, there are some meetings taking place prior to that - see below.

Best,
Jonas

This Week in Logic at CUNY:

- - - - Monday, Jan 17, 2022 - - - -



- - - - Tuesday, Jan 18, 2022 - - - -



- - - - Wednesday, Jan 19, 2022 - - - -



- - - - Thursday, Jan 20, 2022 - - - -



- - - - Friday, Jan 21, 2022 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, January 21, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Wolfgang Wohofsky, University of Vienna
Distributivity spectrum and fresh functions: Part II

We discuss different notions of a distributivity spectrum of forcings.

In the first talk, I will mainly focus on the notion of fresh functions and the corresponding spectrum. A function with domain lambda is fresh if it is new but all its initial segments are in the ground model. I will give general facts how to compute the fresh function spectrum, also discussing what sets are realizable as a fresh function spectrum of a forcing. Moreover, I will provide several examples, including well-known tree forcings on omega such as Sacks and Mathias forcing, as well as Prikry and Namba forcing to illustrate the difference between fresh functions and fresh subsets.

In the second talk, I will also discuss another ('combinatorial') distributivity spectrum; most importantly, analyzing this notion for the forcing P(omega)/fin.

This is joint work with Vera Fischer and Marlene Koelbing.






Next Week in Logic at CUNY:

- - - - Monday, Jan 24, 2022 - - - -



- - - - Tuesday, Jan 25, 2022 - - - -



- - - - Wednesday, Jan 26, 2022 - - - -



- - - - Thursday, Jan 27, 2022 - - - -



- - - - Friday, Jan 28, 2022 - - - -



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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(KGRC) Set Theory Seminar talk on Tuesday, January 18

Kurt Godel Research Center
The KGRC welcomes as guest: Gunter Fuchs (host: Vera Fischer) will visit the KGRC from January 17 to January 20 and give a talk (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 18 "Blurry definability" Gunter Fuchs (City University of New York, USA) In this talk on ongoing research, I analyze blurry forms of ordinal definability and their hereditary versions which generalize ideas due to Hamkins/Leahy and Tzouvaras. Classically, a set is ordinal definable if it is the _unique_ object satisfying some first order property in which ordinal parameters may occur. Given a cardinal kappa, I define that a set is

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday January 19th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie-Hanson -- Variations on theorems of Silver and Galvin-Hajnal We will begin by reviewing the celebrated theorems of Silver and Galvin-Hajnal about cardinal exponentiation at singular cardinals of uncountable cofinality. We will then present some recent variations on these theorems concerning cardinal characteristics at singular cardinals, focusing in particular on the dominating number. Also, there is a small online set theory conference tomorrow (Friday), see https://www1.maths.leeds.ac.uk/~pmtadb/STUK7/STUK7.html Best, David

Logic Seminar Talk 19 Jan 2022 16:00 hrs at NUS over Zoom by Ye Jinhe

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 19 January 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Ye Jinhe, Institut de Mathematiques de Jussieu - Paris Rive Gauche Title: Curve-Excluding Fields Abstract: Consider the class of fields with Char(K)=0 and x^4+y^4=1 has only 4 solutions in K, we show that this class has a model companion, which we denote by curve-excluding fields. Curve-excluding fields provides (counter)examples to various questions. Model theoretically, they are model complete. Field theoretically, they are not large and unbounded. Time permitting, we will discuss other aspects such as decidability of such fields. Joint work with Will Johnson and Erik Walsberg. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

World Logic Day Event // January 14

Set Theory Seminar at the Fields Institute
January 14th is World Logic Day, as designated by the UNSECO, see On this day the Toronto Set Theory Seminar at the Fields Institute will hold a special session with 5 short talks (20 minutes each), showcasing recent research by faculty and postdocs at University of Toronto: ==================================================================== Friday January 14 at the Set Theory Seminar (Fields Institute, Toronto): Location: https://zoom.us/j/92701726800 ==================================================================== 13:30 Ivan Ongay-Valverde and Franklin D. Tall﹡: A New Topological Generalization of Descriptive Set Theory We generalize the K-analytic spaces to the K-σ-projective spaces. We get an application to Selection Principles: Theorem. The Axiom of σ-Projective Determinacy implies every K-σ-projective Menger space is Hurewicz. -------------------------------------------------------------------- 13:50 Ivan Ongay Valverde﹡ and Franklin D. Tall: Upper semi-continuous compact-valued functions and the K-sigma-projective hierarchy Completing the previous talk, we introduce USCCV functions (actually, multifunctions), which were employed in the study of K-analytic spaces, and show how to use them to prove the crucial: Theorem. K-σ-projective spaces are projectively σ-projective. -------------------------------------------------------------------- 14:10 Christopher J. Eagle, Clovis Hamel﹡, Sandra Müller, and Franklin D. Tall: An undecidable extension of Morley's theorem on the number of countable models Morley’s theorem states that the number of non-isomorphic countable models of a complete countable first-order theory in a countable language is ℵ0 or ℵ1 or 2ℵ0. Vaught’s conjecture remains one of the most important open problems in Model Theory, asking whether ℵ1 can be omitted in the conclusion of Morley’s theorem. Even though Vaught’s conjecture is trivially false in second-order logic, no result was known regarding Morley’s trichotomy for second-order logic. We shall show using forcing, large cardinals and descriptive set theory that the second-order version of Morley’s theorem is undecidable. -------------------------------------------------------------------- 14:30 Andrew Marks and Spencer Unger﹡: Flows on the torus In joint work with Andrew Marks, we gave a constructive solution to Tarski's circle squaring problem. In particular, we showed that a disk and a square with the same area are equidecomposible using translations. One important innovation of the proof was to construct a real valued flow from the disk to the square. The notion of flow that we use comes from the study of networks and is related to max flow-min cut. In this talk, I will sketch a simpler construction of a real-valued flow from the disk to the square, which is joint work with Andrew Marks. Using discrepancy estimates due to Laczkovich, this argument works for sets whose boundary has small upper Minkowski dimension. I will also mention ongoing work with Anton Bernshteyn and Anush Tserunyan where we construct a large and diverse collection of flows under the same assumptions. -------------------------------------------------------------------- 14:50 Haosui Duanmu, David Schrittesser﹡, and William Weiss: Infinitesimals and Probabilities In joint work with Haosui Duanmu and William Weiss, we investigate applications of nonstandard analysis in measure theory. The use of infinitesimals and hyperfinite probability spaces offers alternative viewpoints on many classical problems, via Peter Loeb's construction of measures using hyperfinite probability mass functions to construct classical measures. In this talk, I will describe a solution to a problem posed by Keisler, about Loeb measures, and also mention applications in statistics which are joint work with Haosui Duanmu and Daniel Roy. -------------------------------------------------------------------- Find this program also at: For more information about events worldwide see also -- http://homepage.univie.ac.at/david.schrittesser pronouns he/him

(KGRC) (corrected) World Logic Day 2022

Kurt Godel Research Center
(Correction: Parts of the most recent announcement gave the wrong begin time for Victor's talk in the Logic Colloquium. The correct time is 11:30am - apologies for any confusion caused! Below is the corrected text for the announcement.) On January 14th is the World Logic Day. The KGRC is making a small contribution towards the celebrations by dedicating the Tuesday and Thursday seminars next week to it. For more information about events worldwide see https://wld.cipsh.international/background.html * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, January 11 The Set Theory Research Seminar will host five short talks given by masters and doctoral students on topics from their theses. For information regarding the schedule, titles and abstracts see the attached file (the talks are mainly intended for a student audience). Time and Place Talks at 3:00pm via Zoom - see attached file for schedule. If interested contact vera.scher@univie.ac.at. * * * Logic Colloquium Kurt Gödel Research Center Thursday, January 13 "Worlds without Martin's Axiom" Víctor Torres-Pérez (TU Wien) The first of Hilbert's famous list of problems at the beginning of the 20th century was to establish Cantor's Continuum Hypothesis (CH), i.e. if there is no uncountable subset of the reals with cardinality strictly less than the continuum. After the works of Gödel and Cohen, it was concluded that the traditional axioms of Set Theory (ZFC) cannot decide CH. Since then, new axioms have emerged. Prominently we have Forcing Axioms. One of the first Forcing Axioms ever considered was Martin's Axiom (MA). While MA implies the negation of the CH, it does not decide the exact value of the continuum. However, generalizations of MA like the Proper Forcing Axiom (PFA) or Martin's Maximum (MM) do imply that the continuum is the second uncountable cardinal. Besides, PFA or MM imply the negation of certain square principles or tree properties (among a very large number of interesting consequences). This means in particular that these axioms require the existence of large cardinals. There are other relatively new principles, which have strong consequences similar to the ones from PFA or MM, but they can coexist consistently with the absence of MA or even imply this absence. A couple of these principles are, for example, Rado's Conjecture (RC) and the P-Ideal Dichotomy (PID). We will give a general review of results involving these kinds of principles, including some of ours obtained along the previous years. There, it is possible to observe that even if they can avoid MA, they are still quite powerful like these traditional Forcing Axioms. We will expose one of our last results, where we prove (with L. Wu) that PID implies the negation of a certain type of two-cardinals square principle. Time and Place Talk at 11:30am via Zoom - Please note the unusual time! If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!
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Logic Day Special Wed 12 Jan 2022 16:00 hrs SGT

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 12 Jan 2022, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 (1) Logic Day Special For the logic day, everyone is encouraged to present his or her favourate result, which is not required to be recent. Alternatively the participant can also present open questions, perhaps with partial results. Every contribution is welcome. For planning purposes, please email contributions to Frank Stephan (fstephan@comp.nus.edu.sg) and Yang Yue (matyangy@nus.edu.sg). (2) Planning of Logic Seminar At http://www.comp.nus.edu.sg/~fstephan/logicseminar.html you find a schedule of the so far reserved slots. If you are willing to present a talk in the logic seminar (40 - 50 minutes), please select one day which is still free and we will note you down. The timing can be changed if needed. Also if you happen to know of someone who might be interested in giving a talk, please inform us and we will follow up with this person. Frank Stephan (fstephan@comp.nus.edu.sg) Yang Yue (matyangy@nus.edu.sg) Organisers of the Logic Seminar URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar
Dear all, No seminar tomorrow, Wednesday January 5th. The seminar meets again on Wednesday January 12th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: David Uhrik -- Cohen reals and partition relations Abstract: The effect of adding Cohen reals on partition relations will be discussed. Specifically, we will prove that the relation omega_2 --> (omega_2, omega:omega)^2 holds after adding Cohen reals to a model of CH. We will also prove that this result is in a sense best possible. Best, David

21.12.2021 Seminar canceled

IMPAN Working Group in Applications of Set Theory
Due to health issues of several participants we need to cancel the meeting of the seminar tomorrow 21.12.2021, when Damian Sobota was supposed to speak. We are very sorry. The talk will be postponed for March/April 2022. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/ ----- Em 18 de Dez de 2021, em 13:35, Piotr Koszmider piotr.koszmider@impan.pl escreveu: | Seminar: Working group in applications of set theory, IMPAN | | Tuesday, 21.12.2021, 13.30, room 403 | | Speaker: Damian Sobota (KGRC, Vienna) | | Title: "Measures with the Additive Property and the random forcing" | | Abstact: "Let μ be a finitely additive probability measure on ω which vanishes | on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is | not σ-additive, however it may be almost σ-additive in the following weak | sense. We say that μ has the Additive Property, (AP) in short, if for every | sequence (An) of pairwise disjoint subsets of ω there is a subset A such that | A_n\A is finite for every n∈ω and μ(A)=Σn μ(A_n). Equivalently, for every | decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n | is finite for every n∈ω and μ(A)=limn μ(A_n). The latter definition implies | immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the | one-point measure δ_U has (AP). And similarly as in the case of P-points the | existence of measures with (AP) is independent of ZFC. | | During my talk I will discuss basic properties of (families of) measures with | (AP) as well as show, at least briefly, that using old ideas of Solovay and | Kunen one can obtain a non-atomic measure with (AP) in the random model. The | latter result implies that in this model there exists a ccc P-set in ω*, which | may be treated as a (weak) partial answer to the question asking whether there | are P-points in the random model. | | This is a joint work with Piotr Borodulin-Nadzieja." | | |

Damian Sobota, Measures with the Additive Property and the random forcing

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 21.12.2021, 13.30, room 403 Speaker: Damian Sobota (KGRC, Vienna) Title: "Measures with the Additive Property and the random forcing" Abstact: "Let μ be a finitely additive probability measure on ω which vanishes on points, that is, μ({n})=0 for every n∈ω. It follows immediately that μ is not σ-additive, however it may be almost σ-additive in the following weak sense. We say that μ has the Additive Property, (AP) in short, if for every sequence (An) of pairwise disjoint subsets of ω there is a subset A such that A_n\A is finite for every n∈ω and μ(A)=Σn μ(A_n). Equivalently, for every decreasing sequence (A_n) of subsets of ω there is a subset A such that A\A_n is finite for every n∈ω and μ(A)=limn μ(A_n). The latter definition implies immediately that, e.g., an ultrafilter U on ω is a P-point if and only if the one-point measure δ_U has (AP). And similarly as in the case of P-points the existence of measures with (AP) is independent of ZFC. During my talk I will discuss basic properties of (families of) measures with (AP) as well as show, at least briefly, that using old ideas of Solovay and Kunen one can obtain a non-atomic measure with (AP) in the random model. The latter result implies that in this model there exists a ccc P-set in ω*, which may be treated as a (weak) partial answer to the question asking whether there are P-points in the random model. This is a joint work with Piotr Borodulin-Nadzieja." Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 22nd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. We will have Jan Grebik as a guest (speaker). Best, David

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

This will be the final mailing of This Week In Logic for the semester - we will resume in early January.  Happy Holidays to all!

Jonas


This Week in Logic at CUNY:

- - - - Monday, Dec 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 13, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Cezary Cieśliński, University of Warsaw
On the principle of disjunctive correctness

The disjunctive correctness principle (DC) states that a disjunction of arbitrary (possibly nonstandard) length is true if and only if one of its disjuncts is true. On first sight, the principle seems an innocent and natural generalization of the familiar compositional truth axiom for disjunction. However, Ali Enayat and Fedor Pakhomov demonstrated that (DC) has the same strength as Delta_0 induction, hence it produces a non-conservative extension of the background arithmetical theory.

In the presentation the proof of a stronger result will be presented. Let (DC-Elim) be just one direction of (DC), namely, the implication 'if a disjunction is true, then one of it disjuncts is true'. We will show that already (DC-Elim) carries the full strength of Delta_0 induction; moreover, the proof of this fact will be significantly simpler than the original argument of Enayat and Pakhomov.




Logic and Metaphysics Workshop
Date: Monday, December 13th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dolf Rami (Bochum)
Title: Singular existentials and three different kinds of negation

Abstract: In this paper, I will argue for a new semantic analysis of (i) singular existential and (ii) atomic sentences to be able to cover three possible types of negation of them. Firstly, I will show that all three negations of sentences of kind (i) are equivalent if we make use of referring or non-referring names, while on the other hand the three negations of sentences of kind (ii) have several non-equivalent readings if non- referring names are used. Secondly, I will review the partial solutions to our problem given by Russell, Quine and Sainsbury and show in how far they fail. Thirdly, I will propose an alternative solution based on a semantics outlined in Rami (2020). Finally, I will show that we must distinguish two types of negation and that a unification in both directions fails.




- - - - Tuesday, Dec 14, 2021 - - - -

Computational Logic seminar
Tuesday December 14, 2021, 2-4pm, Eastern Time US
Contact sartemov@gc.cuny.edu for a zoom link
Speaker: V. Alexis Peluce, CUNY Graduate Center
Title: Explicit Modal Logic as the Structure of Relevance

Abstract. Orlov and Gödel pioneered the method of syntactic translation of propositional formulas into modal language. Justification Logic takes this a step further by revealing the explicit content of individual modalities. Sergei Artemov extended Gödel's work by showing that S4 can be interpreted in the Logic of Proofs, which can in turn be interpreted in terms of arithmetical proof predicates, thereby providing a rigorous arithmetical foundation for constructivism.

In this work, we examine Classical Logic through the Gödel-Artemov lens. The paradoxes of material implication are a family of classical implications that diverge in meaning from the natural language conditional. We present seven such paradoxes, translate them into S5|the natural modal counterpart of CPC|and then populate the resulting S5 formulas with explicit modalities. We show that for each of our paradoxes, there is a corresponding explicit, non-paradoxical formula. This, we suggest, provides a general method for solving the paradoxes of material implication.




- - - - Wednesday, Dec 15, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Samantha Jarvis, The CUNY Graduate Center.
Date and Time:     Wednesday December 15, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
TBA


- - - - Thursday, Dec 16, 2021 - - - -



- - - - Friday, Dec 17, 2021 - - - -



Next Week in Logic at CUNY:

- - - - Monday, Dec 20, 2021 - - - -



- - - - Tuesday, Dec 21, 2021 - - - -



- - - - Wednesday, Dec 22, 2021 - - - -



- - - - Thursday, Dec 23, 2021 - - - -



- - - - Friday, Dec 24, 2021 - - - -


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Agnieszka Widz, Magic Sets

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 14.12.2021, 13.30, room 403 Speaker: Agnieszka Widz (Lodz University of Technology) Title: Magic Sets Abstact: Given a family of real functions F we say that a set M ⊆ ℝ is magic for F if for all f, g ∈ F we have f [M ] ⊆ g[M ] ⇒ f = g. This notion was introduced by Diamond, Pomerance and Rubel in 1981 [1]. Recently some results about magic sets were proved by Halbeisen, Lischka and Schumacher [2]. Inspired by their work I constructed two families of magic sets one of them being almost disjoint and the other one being independent. During my talk I will sketch the background and present the proof for the independent family, which uses a Kurepa tree. References: [1] H. G. Diamond, C. Pomerance, L. Rubel, Sets on which an entire function is determined by its range, Mathematische Zeitschrift, 176 (1981), 383-398. [2] L. Halbeisen, M. Lischka, S. Schumacher, Magic Sets, Real Anal. Exchange, 43 (2018), 187-204. Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Luca Motto-Ros (Torino)
TITLE: Generalized Polish spaces at reguulart uncountable cardinals
DATE: 15 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 15th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program; we will have another attempt at: Adam Bartoš -- KPT correspondence in the context of weak Fraïssé categories (continued) Last time we formulated the KPT correspondence theorem in our setting, and summarized abstract Fraïssé theory in our setting. Next time we discuss the weak amalgamation property, the (weak) Ramsey property in the abstract setting, recall extreme amenability, and prove the main theorem. If time permits, we mention applications for strong trees. Best, David

(KGRC) four talks on Tuesday, December 14 and one talk on Thursday, December 16

Kurt Godel Research Center
Note: Effective December 14, the password for the Set Theory Research Seminar changes (again); if you have not received the meeting link(s) by the day before the talk, please contact richard.springer@univie.ac.at! * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, December 14 The Set Theory Research Seminar on December 14th, 2021 will feature four talks given by doctoral students. Julia Millhouse and Lukas Schembecker will give 25 minute expository talks on selected topics. Marlene Koelbing and Yuxin Zhou, who are graduating doctoral students at University of Vienna and University of Florida, respectively, will give 50 minute presentations on results from their dissertations. For the schedule of the talks, titles and abstracts, please see the attached file. The Zoom link and Meeting ID will stay the same, but the password will change. If there are any questions, please direct them to vera.fischer@univie.ac.at! * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 16 "Classification of definable quotients" Martin Hils (Universität Münster, Germany) In many areas of mathematics, quotient objects play an important role, and it is often useful to close a category under quotients. In the talk, we will discuss so-called imaginaries, i.e., definable quotients in first order logic. In algebraically closed and in real closed fields, imaginaries may be eliminated. In valued fields, the situation is more interesting, as there are definable quotients like the residue field and value group which may not be eliminated. In algebraically closed valued fields, the imaginaries were classified by Haskell-Hrushovski-Macpherson. We will discuss a recent generalization of their work to more general henselian valued fields, which is joint with Silvain Rideau-Kikuchi. Time and Place Talk at 3:00pm via Zoom - if you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!
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Mirna Dzamonja @ Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: Morass-generic structures Speaker: Mirna Dzamonja, IRIF (CNRS-Université deParis) Date and Time: Friday, December 10, 2021 - 13:30 to 15:00 (Toronto time) Abstract: We discuss a joint work with Wiesław Kubiś on a specific way of constructing structures of size ℵ1 using finite approximations, namely by organising the approximations along a simplified morass. We demonstrate a connection with Fraïssé limits and show that the naturally obtained structure of size ℵ1 is homogeneous. Moreover, this is preserved under expansions, which leads us to a partial answer to a question of Bassi and Zucker. We give some examples of interesting structures constructed, such as the antimetric space of size ℵ1. Finally, we comment on the situation when one Cohen real is added. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Dec 6, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 6, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Bartosz Wcisło, Polish Academy of Sciences
Model theoretic characterizations of truth: Part II

This is joint work (still in progress) with Mateusz Łełyk (who gave the first part of the talk). By an axiomatic theory of truth (for the language of arithmetic, ) we mean a theory in L enriched with a fresh unary predicate  which (extends the elementary arithmetic EA and) proves all sentences of the form ( being a sentence in L) 

The collection of all sentence of the above form is normally called . It is well known that axiomatic theories of truth have a number of interesting model-theoretic consequences. For example, already relatively weak theories of truth impose recursive saturation, in the sense that the L-reduct of any model of such theory is recursively saturated. To give another example, already  imposes elementary equivalence of models, in the sense that whenever , and  (the first model is a submodel of the second one), then actually  and  are elementarily equivalent. During (both parts) of the talk we investigate which of these properties actually characterize the respective truth theory up to definability. In particular, in the first part of the talk, we prove the following results (we restrict ourselves to theories in a finite language and extending EA):

  1. Every theory which imposes elementary equivalence defines .
  2. Every theory which imposes full elementarity defines .

Additionally, we take a look at the definability relations between axiomatic truth theories and axiomatic theories of definability or skolem functions.







Logic and Metaphysics Workshop
Date: Monday, December 6th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Diderik Batens (Ghent)
Title: Every Logic has its Proper Semantics

Abstract: Many logics are sound and complete with respect to a multiplicity of semantic systems. These assign different sets of models to the logic. It will be shown that a series of problems result if all these semantic systems are on a par. I shall present a method to define a unique ‘proper’ semantics for the members of a huge class of logics, containing all usual deductive logics, and argue (i) that the proper semantics is defined in terms of syntactic criteria and so depends fully on the logic, (ii) that there are philosophical arguments to consider a logic’s proper semantics as natural, for example it correctly describes the ‘situations’ that are possible according to the logic. This solves the problems mentioned previously. Implications for the discussion on inferentialism are obvious. For some logics, the proper semantics coincides with the Henkin semantics. For other logics L, the proper semantics counts more models than the Henkin semantics: moreover, not all Henkin models are maximally L-non-trivial. A small change to the Henkin method has the effect that, for every logic L, the Henkin semantics coincides with the proper semantics.




- - - - Tuesday, Dec 7, 2021 - - - -



- - - - Wednesday, Dec 8, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Jens Hemelaer, University of Antwerp.
Date and Time:     Wednesday December 8, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
Title:     Toposes of presheaves on a monoid and their points.

Abstract: In 2014, Connes and Consani constructed their Arithmetic Site, with as underlying topos the topos of presheaves on the monoid of nonzero natural numbers under multiplication. One of their surprising results is that the points of this topos are classified by a double quotient of the finite adeles, leading immediately to a link with number theory. Inspired by this, we will consider toposes of presheaves on various monoids, and discuss strategies of calculating their points. The most recent strategies (involving for example étale geometric morphisms and complete spreads) are based on joint work with Morgan Rogers.



- - - - Thursday, Dec 9, 2021 - - - -



- - - - Friday, Dec 10, 2021 - - - -

Seminar in Philosophy, Logic and Game
Friday, December 10, 10:30 AM
A Zoom link will be sent out on December 8 and will also be posted on
https://philog.arthurpaulpedersen.org/ 
Speaker: David Ellerman, University of Ljubljana
"What is Information and How to Measure it?"

Abstract: In view of the duality between subsets and quotient sets (= partitions = equivalence relations), the Boolean logic of subsets (usually presented as "propositional" logic) has a dual logic of partitions. The quantitative version of Boolean logic is the Boole-Laplace notion of logical probability. Gian-Carlo Rota held that probability is to subsets as information is to partitions, so the quantitative version of partition logic is the theory of logical entropy. This talk is an introduction to logical entropy as the natural measure (in the sense of measure theory) of information as distinctions. It is also shown that the Shannon entropy (which is not a measure) is a uniform transform of logical entropy that is a different quantification of the same notion of information as distinctions.





Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, December 10, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Eyal Kaplan, Tel Aviv University
Non-stationary support iterations of Prikry forcings and restrictions of ultrapower embeddings to the ground model, part II

Assume that  is a forcing notion,  is a generic set for it over the ground model , and a cardinal  is measurable in the generic extension. Let  be an ultrapower embedding, taken in  with a normal measure on . We consider the following questions:

1. Is the restriction of  to  an iterated ultrapower of  (by its measures or extenders)?

2. Is the restriction of  to  definable in ?

By a work of Schindler [1], the answer to the first question is affirmative, assuming that there is no inner model with a Woodin Cardinal and  is the core model. By a work of Hamkins [2], the answer to the second question is positive for forcing notions which admit a Gap below .

We will address the above questions in the context of nonstationary-support iteration of Prikry forcings below a measurable cardinal . Assuming GCH only in the ground model, we provide a positive answer for the first question, and describe in detail the structure of  restricted to  as an iteration of . The answer to the second question may go either way, depending on the choice of the measures used in the Prikry forcings along the iteration; we will provide a simple sufficient condition for the positive answer. This is a joint work with Moti Gitik.

[1] Ralf Schindler. Iterates of the core model. Journal of Symbolic Logic, pages 241–251, 2006.

[2] Joel David Hamkins. Gap forcing. Israel Journal of Mathematics, 125(1):237–252, 2001.




Next Week in Logic at CUNY:

- - - - Monday, Dec 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, December 6, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Cezary Cieśliński, University of Warsaw
On the principle of disjunctive correctness

The disjunctive correctness principle (DC) states that a disjunction of arbitrary (possibly nonstandard) length is true if and only if one of its disjuncts is true. On first sight, the principle seems an innocent and natural generalization of the familiar compositional truth axiom for disjunction. However, Ali Enayat and Fedor Pakhomov demonstrated that (DC) has the same strength as Delta_0 induction, hence it produces a non-conservative extension of the background arithmetical theory.

In the presentation the proof of a stronger result will be presented. Let (DC-Elim) be just one direction of (DC), namely, the implication 'if a disjunction is true, then one of it disjuncts is true'. We will show that already (DC-Elim) carries the full strength of Delta_0 induction; moreover, the proof of this fact will be significantly simpler than the original argument of Enayat and Pakhomov.




Logic and Metaphysics Workshop
Date: Monday, December 13th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Dolf Rami (Bochum)
Title: Singular existentials and three different kinds of negation

Abstract: In this paper, I will argue for a new semantic analysis of (i) singular existential and (ii) atomic sentences to be able to cover three possible types of negation of them. Firstly, I will show that all three negations of sentences of kind (i) are equivalent if we make use of referring or non-referring names, while on the other hand the three negations of sentences of kind (ii) have several non-equivalent readings if non- referring names are used. Secondly, I will review the partial solutions to our problem given by Russell, Quine and Sainsbury and show in how far they fail. Thirdly, I will propose an alternative solution based on a semantics outlined in Rami (2020). Finally, I will show that we must distinguish two types of negation and that a unification in both directions fails.




- - - - Tuesday, Dec 14, 2021 - - - -



- - - - Wednesday, Dec 15, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Speaker:     Samantha Jarvis, The CUNY Graduate Center.
Date and Time:     Wednesday December 15, 2021, 7:00 - 8:30 PM., on Zoom (contact noson@sci.brooklyn.cuny.edu for the link)
TBA


- - - - Thursday, Dec 16, 2021 - - - -



- - - - Friday, Dec 17, 2021 - - - -





- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Kacper Kucharski, Overcomplete sets in selected nonseparable Banach spaces

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 7.12.2021, 13.30, room 403 Speaker: Kacper Kucharski (UW) Title: "Overcomplete sets in selected nonseparable Banach spaces" Abstact: "A subset Y of a Banach space X is called overcomplete if |Y|=dens(X) and for any set Z⊆Y, such that |Z|=|Y|, Z is linearly dense in X. A classical result says that every separable Banach space admits an overcomplete set. The main goal of the talk is to show how, using a certain Aronszajn tree, one can step-up this property for selected nonseparable Banach spaces. If there is enough time, one consistency result will also be stated and proved". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Philipp Schlicht (Bristol)
TITLE: Forcing axioms via ground model interpretations
DATE: 8 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Wednesday seminar

Prague Set Theory Seminar
Dear all, Because of an increasing number of covid infections among regular seminar participants, the seminar next week, Wednesday December 8th is cancelled. It is unclear whether the seminar will resume in December, no announcement = no seminar. The expected program for the next seminar is Adam Bartoš finishing his talk on KPT correspondence in the context of weak Fraïssé categories. (This week we had a talk by Chris Lambie-Hanson instead.) Moreover, there are some sad news from Kosice, see attachment. Best, David

(KGRC) Set Theory Research Seminar talk on Tuesday, December 7

Kurt Godel Research Center
Note: The KGRC Set Theory Seminar recently moved to another Zoom meeting (while other KGRC events kept their Zoom meetings). If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, December 7 "On regular countably compact R-rigid spaces" Serhii Bardyla (KGRC) A regular separable first-countable countably compact space is called a Nyikos space. A space $X$ is called R-rigid if any continuous real-valued function on $X$ is constant. Under MA we construct an R-rigid Nyikos space. This way we answer a few questions of Tzannes and extend results of Ciesielski and Wojciechowski. This is a joint work with Zdomskyy. Time and Place Talk at 3:00pm via Zoom - see top of this message

Mariam Beriashvili @ Toronto Set Theory Seminar // UNUSUAL TIME

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: On two-point sets and other nontrivial point sets Speaker: Mariam Beriashvili, I. Vekua Institute of Applied Mathematics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia Date and Time: Friday, December 3, 2021 - 10:00am to 11:30am Abstract: We consider certain pathological point sets from the general measure theoretical point of view. Namely, we discuss Mazurkiewicz sets, also called two-point sets, which have difficult and interesting descriptive as well as measure theoretic properties. Moreover, we will discuss also uniform subsets of the Euclidean space and their connections to the Mazurkiewizc sets. Also, in the talk will be considered Bernstein sets and Hamel bases. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Mariam Beriashvili @ Toronto Set Theory Seminar // UNUSUAL TIME

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Title: On two-point sets and other nontrivial point sets Speaker: Mariam Beriashvili, I. Vekua Institute of Applied Mathematics, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia Date and Time: Friday, December 3, 2021 - 10:00am to 11:30am Abstract: We consider certain pathological point sets from the general measure theoretical point of view. Namely, we discuss Mazurkiewicz sets, also called two-point sets, which have difficult and interesting descriptive as well as measure theoretic properties. Moreover, we will discuss also uniform subsets of the Euclidean space and their connections to the Mazurkiewizc sets. Also, in the talk will be considered Bernstein sets and Hamel bases. Location: https://zoom.us/j/92701726800 ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Menachem Magidor (Jerusalem)
TITLE: Borel canonization of analytic and universally Baire relations
DATE: 1 December 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Piotr Koszmider, Bidiscrete system in compact spaces

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 30.11.2021, 13.30, room 403 Speaker: Piotr Koszmider (IM PAN) Title: "Bidiscrete system in compact spaces" Abstact: "A set X of the square of a compact Hausdorff space K is called bidiscrete if for every (x, y) in X there is a continuous real valued function f on K such that f(x)=1, f(y)=0 and f(x')=f(y') for any (x', y') in X-{(x, y)}. Bidiscrete sets play role in investigations related to biorthogonal systems in Banach spaces and irredundant sets in many algebraic structures induced by the compact K, but the question if there is in ZFC a nonmetrizable compact K with no uncountable bidiscrete set remains open. There are such examples under special set-theoretic assumptions (Kunen) and there are no such totally disconnected examples under other assumptions (Todorcevic). We will discuss these and other know results and open problems.". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks on Tuesday, November 30 and Thursday, December 2

Kurt Godel Research Center
Note: Starting November 30, the Zoom meeting ID and passcode change for the Set Theory Seminar (but remain unchanged for other KGRC seminars). If you have not received the meeting link(s) by the day before the talk, please contact richard.springer@univie.ac.at! (Please direct any other requests pertaining to the Set Theory Seminar and its Zoom meeting to vera.fischer@univie.ac.at.) * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 30 "Big Ramsey degrees of 3-uniform hypergraphs are finite, part 2" David Chodounský (TU Wien) This is a continuation of the KGRC Set Theory seminar talk I gave in June 2021. I will quickly repeat the content of the first talk and focus on things I did not cover then. It is well known that the (universal countable) Rado graph has finite big Ramsey degrees. I.e., given a finite colouring of n-tuples of its vertices there is a copy of the Rado graph such that its n-tuples have at most D(n)-many colours. The proof of this fact uses a theorem of Milliken for trees. I will talk about the extension of this argument which works also for universal structures with higher arities, in particular 3-uniform hypergraphs. Joint work with M. Balko, J. Hubička, M. Konečný, and L. Vena, see https://arxiv.org/abs/2008.00268 Time and Place Talk at 3:00pm via Zoom - see top of this message * * * Logic Colloquium Kurt Gödel Research Center Thursday, December 2 "The world between aleph1 and continuum: from Martin's Axiom to Cichoń's Maximum" Martin Goldstern (TU Wien) Georg Cantor's "Continuum Hypothesis" (CH) postulates that the continuum (the cardinality of the set of real numbers) is equal to aleph1, the smallest uncountable cardinal. Martin's Axiom (MA) is a weakening of CH; it implies that all infinite cardinals below the continuum are similar to aleph0, the cardinality of a countable set. For example, MA implies that not only every countable union of null (measure zero) sets is still null, but even every union of fewer than continuum many such sets. This motivates the definition of a so-called cardinal characteristic, the additivity number of the measure zero sets - the answer to the question "how many null sets do we have to join together to get a non-null set". There is a whole zoo of such cardinal characteristics (some of them defined long before the advent of forcing); whenever you know that any countable set of objects with property X will never have property Y, you may ask how many such objects you need to get to Y. Accepting CH or just MA as an axiom gives a picture that is on the one hand very clean, but on the other hand also rather poor: most cardinal characteristics can then be shown to be equal to the continuum. In my talk I will discuss - or at least hint at - some recent (and some old) techniques for constructing "anti-MA" universes, where many cardinals between omega1 and the continuum appear as cardinal characteristics (defined by some natural properties X and Y). I will try to hide all technical details, so that my talk will hopefully be understandable also for non-set-theorists. Time and Place Talk at 3:00pm via Zoom - see top of this message

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday December 1st at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Adam Bartoš will continue his talk from this week. KPT correspondence in the context of weak Fraïssé categories (continued) Last time we formulated the KPT correspondence theorem in our setting, and summarized abstract Fraïssé theory in our setting. Next time we discuss the weak amalgamation property, the (weak) Ramsey property in the abstract setting, recall extreme amenability, and prove the main theorem. If time permits, we mention applications for strong trees. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Speaker: David Aspero, University of East Anglia Date and Time: Friday, November 26, 2021 - 1:30pm to 2:30pm Location: https://zoom.us/j/92701726800 Abstract: I aim to present the proof that the ℙmax axiom (*) is implied by Martin's Maximum++, as well as some further work related to this result and its proof. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Barcelona Set Theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Chris Scambler (New York University)
TITLE: Axiomatic Potentialism
DATE: 24 November 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Kamil Ryduchowski; A Banach space admitting few operators

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 23.11.2021, 13.30, room 403, (CHANGE OF THE ROOM!) Speaker: Kamil Ryduchowski (MIM UW) Title: "A Banach space admitting few operators" Abstact: "Using the colouring discussed in our previous talk we will construct a Banach space admitting few operators in the following sense: it will be a non-separable Banach space X such that every operator on X is of the form sI + S, where s is a scalar, S is an operator with a separable range and I stands for the identity on X, i.e. every operator on X is a homothety modulo the ideal of operators with separable range. The construction is due to Shelah and Steprans". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) Set Theory Research Seminar talk on Tuesday, November 23

Kurt Godel Research Center
Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 23 "Specializing Triples and Weak Embeddability" Rahman Mohammadpour (TU Wien) A weak embedding between trees is a function that preserves the strict order. A class U of trees is said to be universal for a class C of trees if every tree in C weakly embeds in an element of U. It turns out that the pre-ordered structure induced by weak embeddability on a class C of trees is a plausible tool for the study of the elements of C. One can ask e.g., what is the universality number of a class of trees (the size of the smallest subclass which is universal)? can it be 1? whether a subclass is cofinal? etc. If CH holds, then the class of \aleph_1-wide Aronszan trees (trees of height and size \aleph_1 without cofinal branches) does not have a maximal tree under weak embeddability (this follows from Kurepa's works). Todorcevic has proved, among other things, that under MA_{\aleph_1}, the class of Aronszajn trees has no maximal object. In their joint work on wide Aronszajn trees under MA_{\aleph_1}, Dzamonja and Shelah introduced the notion of a specializing triple that connects weak embeddings to the specialization of trees. In particular, they reproved Todorcevic's result using specializing triples. In this talk, we shall focus on a variant of this notion in a general setting and demonstrate the main aspects of it. We shall then discuss some negative results on the universality problem for Aronszajn trees whose height is the successor of a regular cardinal, and hopefully, we shall finish the talk with some open problems. The results have been obtained in a collaboration with Mirna Dzamonja. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) COVID rules may be accentuated as prompted by the authorities or the university. Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar tomorrow, Wednesday November 17th (state holiday). The seminar meets again on Wednesday November 24th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Adam Bartoš -- KPT correspondence in the context of weak Fraïssé categories The Kechris–Pestov–Todorčević correspondence states that a Fraïssé class of first-order structures has the Ramsey property if and only if the automorphism group of the Fraïssé limit is extremely amenable. We extend this correspondence to weak Fraïssé categories. This is a joint paper with Tristan Bice, Keegan Dasilva Barbosa, and Wiesław Kubiś (https://arxiv.org/abs/2110.01694). At the talk I will give a conceptual overview of the framework, present main ideas of the proofs, and if time permits, give examples in the realm of strong trees. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: ------------------------------------------------------------------- Speaker: Mohammad Golshani, IPM Date and Time: Friday, November 19, 2021 - 1:30pm to 2:30pm Location: https://zoom.us/j/92701726800 Abstract: I will discuss some recent joint projects with Saharon Shelah about the relation between ultraproducts and the continuum hypothesis. In particular, we show that the Keisler's isomorphism theorem implies the continuum hypothesis, and then prove some consistency results in the absence of the continuum hypothesis. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 15, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 15th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Rasmus Blanck, University of Gothenburg
Incompleteness results for arithmetically definable extensions of strong fragments of PA

In this talk, I will present generalisations of some incompleteness results along two axes: r.e. theories are replaced by -definable ones, and the base theory is pushed down as far as it will go below PA. Such results are often easy to prove from suitably formulated generalisations of facts used in the original proofs. I will present a handful of such facts, including versions of the arithmetised completeness theorem and the Orey–Hájek characterisation, to show what additional assumptions our theories must satisfy for the results to generalise. Two salient classes of theories emerge in this context: (a) -sound extensions of I + exp, and (b) -complete, consistent extensions of I. Finally, I will discuss some results that fail to generalise to -definable theories, as well as an open problem related to Woodin's theorem on the universal algorithm.

The presentation is based on the following paper: https://doi.org/10.1017/S1755020321000307




Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 15th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 
Speaker: Sara Uckelman (Durham)
Title: John Eliot’s Logick Primer: A bilingual English-Algonquian logic textbook

Abstract: In 1672 John Eliot, English Puritan educator and missionary, published The Logick Primer: Some Logical Notions to initiate the INDIANS in the knowledge of the Rule of Reason; and to know how to make use thereof [1]. This roughly 80 page pamphlet focuses on introducing basic syllogistic vocabulary and reasoning so that syllogisms can be created from texts in the Psalms, the gospels, and other New Testament books. The use of logic for proselytizing purposes is not distinctive: What is distinctive about Eliot’s book is that it is bilingual, written in both English and Massachusett, an Algonquian language spoken in eastern coastal and southeastern Massachusetts. It is one of the earliest bilingual logic textbooks, it is the only textbook that I know of in an indigenous American language, and it is one of the earliest printed attestations of the Massachusett language. In this talk, I will: (1) Introduce John Eliot and the linguistic context he was working in; (2) Introduce the contents of the Logick Primer—vocabulary, inference patterns, and applications; (3) Discuss notions of “Puritan” logic that inform this primer; (4) Talk about the importance of his work in documenting and expanding the Massachusett language and the problems that accompany his colonial approach to this work.

[1] J.[ohn] E.[liot]. The Logick Primer: Some Logical Notions to initiate the INDIANS in the knowledge of the Rule of Reason; and to know how to make use thereof. Printed by M. J., 1672.




- - - - Tuesday, Nov 16, 2021 - - - -

Computational Logic Seminar
Tuesday November 16, 2021, 2-4pm,  Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Alessandra Palmigiano, Vrije Universiteit Amsterdam
Title: Non-distributive logics: from semantics to meaning.

Abstract: The term ‘non-distributive logics’ refers to the wide family of non-classical propositional logics in which the distributive laws α ∧(β ∨γ) ⊢ (α ∧β)∨(α ∧γ) and (α ∨β)∧(α ∨γ) ⊢ α ∨(β ∧γ) do not need to be valid. Since the rise of very well known instances such as quantum logic, interest in non-distributive logics has been building steadily over the years, motivated by insights from a range of fields in logic and neighbouring disciplines. Techniques and ideas have come from pure mathematical areas such as lattice theory, duality and representation, and areas in mathematical logic such as algebraic proof theory, but also from the philosophical and formal foundations of quantum physics, philosophical logic, theoretical computer science, and formal linguistics.

We will discuss an ongoing line of research in the relational (non topological) semantics of non-distributive logics, which is technically rooted in duality and (generalized) correspondence theory.

Not dissimilarly from the conceptual contribution of Kripke frames to the intuitive understanding of modal logics in various signatures, the relational semantics of non-distributive logics can help to illuminate the intuitive meaning of non-distributive logics at a more fundamental and conceptual level.

We discuss the application of the dual characterization methodology to introduce two relational semantic frameworks for non-distributive logics: the polarity-based frames and the graph-based frames. Despite their common root, polarity-based and graph-based semantics give rise to two radically different intuitive interpretations of non-distributive logics: namely, the polarity-based semantics supports the interpretation of non-distributive logics as logics of categories and formal concepts; the graph-based semantics supports a view of non-distributive logics as hyper-constructivist logics, i.e. logics in which the principle of excluded middle fails at the meta-linguistic level (in the sense that, at states in graph-based models, formulas can be satisfied, refuted or neither), and hence their propositional base generalizes intuitionistic logic in the same way in which intuitionistic logic generalizes classical logic. Consequently, we will argue that graph-based semantics supports the interpretation of non-distributive logics as logics of evidential reasoning.




- - - - Wednesday, Nov 17, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Time: Wednesdays 07:00 PM Eastern Time (US and Canada)
Speaker:     Marco Schorlemmer, Spanish National Research Council.




- - - - Thursday, Nov 18, 2021 - - - -



- - - - Friday, Nov 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna

Definable Well Orders and Other Beautiful Pathologies

Many sets of reals - well orders of the reals, MAD families, ultrafilters on omega etc - only necessarily exist under the axiom of choice. As such, it has been a perennial topic in descriptive set theory to try to understand when, if ever, such sets can be of low definitional complexity. Large cardinals rule out such the existence of projective well orders, MAD families etc while it's known that if  (or even just 'every real is constructible') then there is a  well order of the reals and  witnesses to many other extremal sets of reals such as MAD families and ultrafilter bases. Recently a lot of work on the border of combinatorial and descriptive set theory has focused on considering what happens to the definitional complexity of such sets in models in which the reals have a richer structure - for instance when  fails and various inequalities between cardinal characteristics is achieved. In this talk I will present a recent advance in this area by exhibiting a model where the continuum is , there is a  well order of the reals, and a  MAD family, a  ultrafilter base for a P-point, and a  maximal independent family, all of size . These complexities are best possible for both the type of object and the cardinality hence this may be seen as a maximal model of 'minimal complexity witnesses'. This is joint work with Jeffrey Bergfalk and Vera Fischer.




Next Week in Logic at CUNY:

- - - - Monday, Nov 22, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 22th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mauro di Nasso, Università di Pisa
Nonstandard natural numbers in arithmetic Ramsey Theory and topological dynamics

The use of nonstandard models *N of the natural numbers has recently found several applications in arithmetic Ramsey theory. The basic observation is that every infinite number in *N corresponds to an ultrafilter on N, and the algebra of ultrafilters is a really powerful tool in this field. Note that this notion also makes sense in any model of PA, where one can consider the 1-type of any infinite number.

Furthermore, nonstandard natural numbers are endowed with a natural compact topology, and one can apply the methods of topological dynamics considering the shift operator  . This very peculiar dynamic has interesting characteristics.

In this talk I will also present a new result in the style of Hindman’s Theorem about the existence of infinite monochromatic configurations in any finite coloring of the natural numbers. A typical example is the following monochromatic pattern:
a, b, c,  , a+b+ab, a+c+ac, b+c+bc,  , a+b+c+ab+ac+bc+abc.






Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 22th, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/
Konstantinos Georgatos (John Jay).
Title: Similarity through indistinguishability: the geodesic reasoning on Kripke models

Abstract: Several logical operators, such as conditionals, revision, and merge, are often understood through the selection of most similar worlds. In applications, similarity is expressed with distance and “most similar” translates to “closest” using a distance metric. We shall argue that similarity may arise through an indistinguishability relation between possible worlds and employ the geodesic distance of such a model to measure closeness. This understanding allows us to define a variety of operators that correspond to merging and revising. I will present a few systems and representation results and will show that revision, merging, and conditioning are interdefinable thus, in effect, satisfying the Ramsey test.




- - - - Tuesday, Nov 23, 2021 - - - -



- - - - Wednesday, Nov 24, 2021 - - - -



- - - - Thursday, Nov 25, 2021 - - - -



- - - - Friday, Nov 26, 2021 - - - -




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Kamil Ryduchowski; An antiramsey coloring of pairs

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 16.11.2021, 13.30, room 105, Speaker: Kamil Ryduchowski (MIM UW) Title: "An antiramsey coloring of pairs " Abstact: "We present a fundamental theorem by Todorcevic, stating that there exists a coloring of the complete graph of the first uncountable cardinality in uncountably many colors without an uncountable monochromatic clique. We also discuss other results of Todorcevic of similar nature, which are in some sense multidimensional variants of that coloring". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) seminar talks Tuesday, November 16 and Thursday, November 18

Kurt Godel Research Center
The KGRC welcomes as guest: Radek Honzik (host: Vera Fischer) will visit the KGRC from November 14 to November 19 and give two talks (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 16 "Indestructibility of some compactness principles over models of PFA" Radek Honzik (Charles University in Prague, Czech Republic) Recall that the tree property at a regular cardinal kappa says that every kappa-tree has a cofinal branch, and the weak Kurepa hypothesis at kappa says that there exists a tree of size and height kappa which has at least kappa^+ cofinal branches. We will prove that over any transitive model of PFA, the tree property at omega_2 cannot be destroyed by the single Cohen forcing Add(omega,1) and the negation of the weak Kurepa hypothesis at omega_1 cannot be destroyed by a sigma-centered forcing. We will observe that a model-theoretic principle, Guessing model property (GMP), is enough for the preservation results. GMP can be formulated also for larger cardinals. We will give an application of our result by showing that there is a model in which the negation of the weak Kurepa hypothesis holds at aleph_{omega+1}. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! * * * Logic Colloquium Kurt Gödel Research Center Thursday, November 18 "Compactness at small uncountable cardinals" Radek Honzik (Charles University in Prague, Czech Republic) We will discuss various compactness principles such as stationary reflection, the tree property or Rado conjecture at small cardinals (for instance omega_2). We will give context and motivation for the principles and discuss and compare the main sources of these principles: large cardinals and consequences of forcing axioms. We will focus on indestructibility of these principles with respect to classes of forcing notions, and give some examples (for instance we show that stationary reflection at omega_2 cannot be destroyed by a ccc forcing). Indestructibility is important for investigating connections between compactness and other areas of set theory such as generalized cardinal invariants, and we will mention some applications. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the talk we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Two talks next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, November 16, 2021 Mathematical logic seminar: 3:30 P.M., Online, William Chan, Carnegie Mellon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 Title: Almost Disjoint Families under Determinacy, part 1 Abstract: We will investigate some properties of almost disjoint families and the maximal almost disjoint (MAD) family problem on cardinals (regular and singular) within determinacy settings. We will show under suitable assumptions that every almost disjoint family on a cardinal of uncountable cofinality must be wellorderable. This will show under suitable assumptions (which includes the boldface GCH) that there are no MAD families on a regular cardinal kappa so that the family does not strictly inject into kappa. (This answers a question of Muller concerning uncountable MAD families on omega_1 under AD.) We will show under AD that every wellorderable almost disjoint family on a cardinal below Theta of countable cofinality is not maximal. This result may help explain why the Schrittesser-Tornquist or Neeman-Norwood arguments excluding a MAD family on omega has quite a different flavor than the MAD family question for cardinals of uncountable cofinality. We will review the ultrapower representation and measure analysis of Jackson below omega_omega. This will be used to investigate the MAD family question surrounding omega_1, omega_2, and the singular cardinals omega_n for n between 3 and omega. This is joint work with Stephen Jackson and Nam Trang. TUESDAY, November 16, 2021 Set Theory Reading Group: 4:30 P.M., Online, William Chan, Carnegie Mellon University Title: Almost Disjoint Families under Determinacy, part 2 Abstract: We will investigate some properties of almost disjoint families and the maximal almost disjoint (MAD) family problem on cardinals (regular and singular) within determinacy settings. We will show under suitable assumptions that every almost disjoint family on a cardinal of uncountable cofinality must be wellorderable. This will show under suitable assumptions (which includes the boldface GCH) that there are no MAD families on a regular cardinal kappa so that the family does not strictly inject into kappa. (This answers a question of Muller concerning uncountable MAD families on omega_1 under AD.) We will show under AD that every wellorderable almost disjoint family on a cardinal below Theta of countable cofinality is not maximal. This result may help explain why the Schrittesser-Tornquist or Neeman-Norwood arguments excluding a MAD family on omega has quite a different flavor than the MAD family question for cardinals of uncountable cofinality. We will review the ultrapower representation and measure analysis of Jackson below omega_omega. This will be used to investigate the MAD family question surrounding omega_1, omega_2, and the singular cardinals omega_n for n between 3 and omega. This is joint work with Stephen Jackson and Nam Trang.

Logic Seminar 10 Nov 2021 16:00 hrs by Manat Mustafa, Nazarbayev University, Kazakhstan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 10 November 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Manat Mustafa Title: Rogers semilattices of punctual numberings URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: The talk employs the punctuality paradigm in the studies of numberings. We consider the punctual numberings, i.e. uniform computations for families of primitive recursive functions. The punctual reducibility between numberings is induced by primitive recursive functions. This approach gives rise to upper semilattices of degrees, which are called Rogers pr-semilattices. The main focus of the talk will be the structural properties of Rogers pr-semilattices. We will show several examples, which highlight further contrasts between the punctual framework and the classical theory of computable numberings. All results are obtained in joint work with Nikolay Bazhenov and Sergei Ospichev.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 8, 2021 - - - -

Logic and Metaphysics Workshop
Date: Tomorrow, Monday, November 8th, 4.15-6.15 (NY time)
Speaker: Roman Kossak (CUNY GC)
Title: How undefinable is truth?

Abstract: Almost any set of natural numbers you can think of is first-order definable in the standard model of arithmetic. A notable exception is the set Tr of Gödel numbers of true first-order sentences about addition and multiplication. On the one hand—by Tarski’s undefinability of truth theorem—Tr has no first order definition in the standard model; on the other, it has a straightforward definition in the form of an infinite disjunction of first order formulas. It is definable in a very mild extension of first-order logic. In 1963, Abraham Robinson initiated the study of possible truth assignments for sentences in languages represented in nonstandard models of arithmetic. Such assignments exist, but only in very special models; moreover they are highly non-unique, and—unlike Tr—they are not definable any  reasonable formal system. In the talk, I will explain some model theory behind all that and I will talk about  some recent results in the study of axiomatic theories of truth.





- - - - Tuesday, Nov 9, 2021 - - - -


Computational Logic Seminar
Tuesday November 9, 2021, 2-4pm,  Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Tuesday November 9, 2021.

Speaker: Antonis Achilleos, Reykjavik University
Title: Adventures in Monitorability

Abstract:
I will present recent work on runtime monitorability. Runtime Verification (RV) is the technique of using a monitor to detect the violation or satisfaction of a property at runtime. One question that we ask is what properties we can monitor for. But even before giving an answer, we must first understand what that question means. Although many monitorability definitions exist, few are defined explicitly in terms of the operational guarantees provided by monitors, ie, the computational entities carrying out the verification. We view monitorability as a spectrum, where the fewer guarantees that are required of monitors, the more properties become monitorable. Accordingly, we present a monitorability hierarchy based on this trade-off..
For regular, linear-time specifications, we give syntactic characterisations of the hierarchy in Hennessy-Milner logic with recursion. 

We then compare the obtained fragments with previous results for the branching-time setting.

This is joint work with Luca Aceto, Adrian Francalanza, Anna Ingólfsdóttir, and Karoliina Lehtinen.





- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 1pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.





Next Week in Logic at CUNY:

- - - - Monday, Nov 15, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, November 15th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Rasmus Blanck, University of Gothenburg
Incompleteness results for arithmetically definable extensions of strong fragments of PA

In this talk, I will present generalisations of some incompleteness results along two axes: r.e. theories are replaced by -definable ones, and the base theory is pushed down as far as it will go below PA. Such results are often easy to prove from suitably formulated generalisations of facts used in the original proofs. I will present a handful of such facts, including versions of the arithmetised completeness theorem and the Orey–Hájek characterisation, to show what additional assumptions our theories must satisfy for the results to generalise. Two salient classes of theories emerge in this context: (a) -sound extensions of I + exp, and (b) -complete, consistent extensions of I. Finally, I will discuss some results that fail to generalise to -definable theories, as well as an open problem related to Woodin's theorem on the universal algorithm.

The presentation is based on the following paper: https://doi.org/10.1017/S1755020321000307





- - - - Tuesday, Nov 16, 2021 - - - -



- - - - Wednesday, Nov 17, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
Time: Wednesdays 07:00 PM Eastern Time (US and Canada)
Speaker:     Marco Schorlemmer, Spanish National Research Council.




- - - - Thursday, Nov 18, 2021 - - - -



- - - - Friday, Nov 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it.

SPEAKER:   Yaroslav D. Sergeyev (University of Calabria)
TITLE: Some paradoxes of Infinity revisited
DATE: 10 November 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.







Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


(KGRC) Set Theory Research Seminar talk on Tuesday, November 9

Kurt Godel Research Center
The KGRC welcomes as guests: Jaroslav Šupina (host: Serhii Bardyla) will stay until November 9. Fortunato Maesano (host: Lyubomyr Zdomskyy) will stay until June 30, 2022. * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, November 9 "The Special Tree Number" Corey Switzer (KGRC) A tree $T$ of height $\omega_1$ with no uncountable branch is {\em special} if there is a function $f:T \to \omega$ which is injective on chains. It's well known that under $\mathrm{MA} + \neg \CH$ every tree of height $\omega_1$ with no uncountable branch of size less than the continuum is special, while in $\mathrm{ZFC}$ one can construct a non-special tree of height $\omega_1$ with no uncountable branch. At the same time there may be a Souslin tree while the continuum is as large as you like thus providing a model with a small non-special tree. These facts together suggest a new cardinal characteristic, the special tree number, denote $\mathfrak{st}$: the least size of a tree of height $\omega_1$ with no uncountable branch which is not special. By what was observed above, $\mathrm{MA} + \neg \CH$ implies that $\mathfrak{st} = 2^{\aleph_0}$ while it is consistent that $mathfrak{st} < 2^{\aleph_0}$ with the latter arbitrarily large. In this talk we will introduce the basic properties of $\mathfrak{st}$ and prove in particular that it is consistent on the one hand that $\mathfrak{st}$ is $\aleph_1$ while essentially all well-studied cardinal characteristics are arbitrarily large and on the other hand it is consistent that for any regular $\kappa$ we have $\mathfrak{a} = {\rm non}(\mathcal M) = \aleph_1 < \mathfrak{st} = {\rm cov}(\mathcal M) = 2^{\aleph_0} = \kappa$. In other words, $\mathfrak{st}$ is independent of the lefthand side of Cicho\'{n}'s diagram, $\mathfrak{p}$ and $\mathfrak{a}$. The latter model involves a careful analysis of reals added by the standard ccc forcing to specialize trees, which may be of independent interest. This is a relatively new investigation and there are many open questions I hope to discuss as well, time permitting. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the lectures we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Please note that tomorrow's Set Theory Seminar meeting starts at 1pm (not 2pm as stated in the previous email).

Best,
Jonas


This Week in Logic at CUNY:

- - - - Friday, Nov 5, 2021 - - - -

Philog Seminar
Friday, November 5, 2021, 10:30 AM (New York time)
(Zoom link will be posted on https://philog.arthurpaulpedersen.org/)
Sonja Smets, University of Amsterdam
Title: Computing Social Behavior
 
Abstract:  Recently, epistemic-social phenomena have received more attention from the logic community, analyzing peer pressure, studying informational cascades, inspecting priority-based peer influence, modeling diffusion and prediction, and examining reflective social influence. In this presentation, I will contribute to this line of work and focus in particular on the logical features of social group creation. I pay attention to the mechanisms which indicate when agents can form a team based on the correspondence in their set of features (behavior, opinions, etc.). Our basic approach uses a semi-metric on the set of agents, which is used to construct a network topology. This structure is then extended with epistemic features to represent the agents' epistemic states, allowing us to explore group-creation alternatives where what matters is not only the agent's differences but also what they know about them. The logical settings in this work make use of the techniques of dynamic epistemic logic to represent group-creation actions, to define new languages in order to describe their effects, and to provide sound and complete axiom systems. This talk is based on joint work with Fernando Velazquez Quesada.

Sonja Smets is a Belgian and Dutch logician and epistemologist known for her work in belief revision and quantum logic. She is Professor of Logic and Epistemology at the University of Amsterdam, where she directed the university's Institute for Logic, Language and Computation and is affiliated with both the Faculty of Science and the Department of Philosophy.




Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 5, 2pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.








Next Week in Logic at CUNY:

- - - - Monday, Nov 8, 2021 - - - -



- - - - Tuesday, Nov 9, 2021 - - - -



- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 1pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 10th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Paul Szeptycki -- An example from a square-sequence, convergence and the G_delta-topology, part 2. Questions of Bella concerning cardinal invariants of the G_delta topology and questions of Arhangel'skii on strong convergence properties are answered with examples constructed from square(kappa) sequences. Best, David

Toronto Set Theory Seminar

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar at the Fields Institute: https://zoom.us/j/92701726800 Friday, November 5, 2021 - 12:30pm to 2:00pm ------------------------------------------------------------------- Speaker: Philip Welch, University of Bristol Title: The universe constructed from a set (or class) of regular cardinals. Abstract: We continue some work on L[Card] (the universe constructed from the predicate for the cardinals) to look at L[Reg] where Reg is the class of uncountable regular cardinals. The latter is also a model of a rich combinatorial structure being, as it turns out, a Magidor iteration of Prikry forcings (using recent work of Ben-Neria). But it is limited in size, in fact is a rather 'thin' model. We show, letting O^s = O^sword be the least iterable structure with a measure which concentrates on measurable cardinals: Theorem (ZFC) (a) Let S be a set, or proper class, of regular cardinals, then O^s is not an element of L[S]. (b) This is best possible, in that no smaller mouse M can be substituted for O^s. (c) L[S] is a model of: GCH, Square's, Diamonds, Morasses etc and has Ramsey cardinals, but no measurable cardinals. ------------------------------------------------------------------- http://www.fields.utoronto.ca/activities/21-22/set-theory-seminar

Toronto Set Theory Seminar // Nov 5 UNUSUAL TIME 12:30 // Philip Welch

Set Theory Seminar at the Fields Institute
Dear All, I would like to invite you to this week's Toronto Set Theory Seminar at the Fields Institute. Careful, we start early this week, at 12:30 ! https://zoom.us/j/92701726800 ----- Speaker: Philip Welch, University of Bristol Date and Time: Friday, November 5, 2021 - 12:30pm to 2:00pm Title: The universe constructed from a set (or class) of regular cardinals. Abstract: We continue some work on L[Card] (the universe constructed from the predicate for the cardinals) to look at L[Reg] where Reg is the class of uncountable regular cardinals. The latter is also a model of a rich combinatorial structure being, as it turns out, a Magidor iteration of Prikry forcings (using recent work of Ben-Neria). But it is limited in size, in fact is a rather 'thin' model. We show, letting O^s = O^sword be the least iterable structure with a measure which concentrates on measurable cardinals: Theorem (ZFC) (a) Let S be a set, or proper class, of regular cardinals, then O^s is not an element of L[S]. (b) This is best possible, in that no smaller mouse M can be substituted for O^s. (c) L[S] is a model of: GCH, Square's, Diamonds, Morasses etc and has Ramsey cardinals, but no measurable cardinals. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

Oct 15 // Toronto Set Theory Seminar // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, The Toronto Set Theory Seminar is resuming; I would like to invite you to our next talk! Friday Oct 15, 13:30 Eastern Daylight Time (GMT-4) at https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω). ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

Oct 15 // Toronto Set Theory Seminar // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
This week at the Toronto Set Theory Seminar Friday Oct 15, 13:30 Eastern Daylight Time (GMT-4) https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω).

Oct 15 9am // Yinhe Peng - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, Sorry, my last email had a wrong starting time. Yinhe's talk will be at 9am ! That is, Friday Oct 15, 9:00 am Eastern Daylight Time (GMT-4) at https://zoom.us/j/92701726800 ----- Speaker: Yinhe Peng, Chinese Academy of Science Title: On Scheepers' conjecture and Scheepers' Diagram Abstract: We first refute Scheepers' conjecture. More precisely, we prove the following: Assuming CH, there is a subset of reals X such that C_p(X) has property (α_2) and X does not satisfy S_1(Γ,Γ). It is known that by Dow and Hales' results, Scheepers' conjecture is consistent. So some additional assumption is needed. We will reveal the idea and some details. All but two implications are known in Scheepers Diagram. We then complete Scheepers Diagram by proving the following: U_fin(Γ,Γ) implies S_fin(Γ,Ω). U_fin(Γ,Ω) does not imply S_fin(Γ,Ω). More precisely, assuming CH, there is a subset of reals X satisfying U_fin(Γ,Ω) such that X does not satisfy S_fin(Γ,Ω). ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

TOMORROW // Toronto Set Theory Seminar // Stefan Hoffelner - On Scheepers' conjecture and Scheepers' Diagram

Set Theory Seminar at the Fields Institute
Dear All, Please allow me to invite you to tomorrow's Toronto Set Theory Seminar at the Fields Institute, at https://zoom.us/j/92701726800 ----- Speaker: Stefan Hoffelner, University of Münster Date and Time: Friday, October 29, 2021 - 1:30pm to 3:00pm Title: Forcing and the Separation, the Reduction and the Uniformization property. Abstract: The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses on the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, Π12n+1 -sets and hence Σ12n+2 -sets do have the Uniformization property (and therefore the weaker Reduction property and the Separation property for the dual pointclass). Yet the question of universes which display an alternative behaviour of theses regularity properties has remained a complete mystery, mostly due to the absence of forcing techniques to produce such models. Indeed, even the question of the forceability of a universe where the Σ13 Separation property holds was a well-known open problem since 1968. In my talk, I want to outline some recently obtained techniques, which turn the question of a universe with, say, the Π13 Reduction property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Π1n Reduction property or, with more complicated techniques, the Π1n Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes outright contradict the PD-induced pattern, for odd n these universes give new lower bounds in terms of consistency strength. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

TOMORROW // Toronto Set Theory Seminar // Stefan Hoffelner // Forcing and the Separation, the Reduction and the Uniformization-property

Set Theory Seminar at the Fields Institute
Dear All, Correction: Now with correct title in the subject line, sorry about that! https://zoom.us/j/92701726800 ----- Speaker: Stefan Hoffelner, University of Münster Date and Time: Friday, October 29, 2021 - 1:30pm to 3:00pm Title: Forcing and the Separation, the Reduction and the Uniformization property. Abstract: The Separation property, the Reduction property and the Uniformization property, introduced in the 1920's and 1930's are three classical regularity properties of pointclasses on the reals. The celebrated results of Y. Moschovakis on the one hand and D. Martin, J. Steel and H. Woodin on the other, yield a global description of the behaviour of these regularity properties for projective pointclasses under the assumption of large cardinals. In particular, under PD, for every natural number n, Π12n+1 -sets and hence Σ12n+2 -sets do have the Uniformization property (and therefore the weaker Reduction property and the Separation property for the dual pointclass). Yet the question of universes which display an alternative behaviour of theses regularity properties has remained a complete mystery, mostly due to the absence of forcing techniques to produce such models. Indeed, even the question of the forceability of a universe where the Σ13 Separation property holds was a well-known open problem since 1968. In my talk, I want to outline some recently obtained techniques, which turn the question of a universe with, say, the Π13 Reduction property into a fixed point problem for certain sets of forcing notions. This fixed point problem can be solved, yielding a specific set of forcing notions which in turn can be used to force the Π1n Reduction property or, with more complicated techniques, the Π1n Uniformization property (for n>2) over fine structural inner models with large cardinals (for n=3, the inner model is just L). For even n, these universes outright contradict the PD-induced pattern, for odd n these universes give new lower bounds in terms of consistency strength. ---- best wishes, David http://homepage.univie.ac.at/david.schrittesser

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Nov 1, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, October 25th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Fedor Pakhomov Ghent University
Finitely Axiomatized Theories Lack Self-Comprehension

This is a joint work with Albert Visser. We prove that no consistent finitely axiomatized theory one-dimensionally interprets its own extension with predicative comprehension. This constitutes a result with the flavor of the Second Incompleteness Theorem whose formulation is completely arithmetic-free. Probably the most important novel feature that distinguishes our result from the previous results of this kind is that it is applicable to arbitrary weak theories, rather than to extensions of some base theory. The methods used in the proof of the main result yield a new perspective on the notion of sequential theory, in the setting of forcing-interpretations. https://arxiv.org/abs/2109.02548 




Logic and Metaphysics Workshop
Date: Monday, November 1, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 
Thomas M Ferguson (Amsterdam)
The Subject-Matter of Modal Sentences

The framework of topic-sensitive intentional modal operators (TSIMs) described by Berto provides a general platform for representing agents' intentional states of various kinds. For example, a TSIM can model doxastic states, capturing a notion that given the acceptance of antecedent information P, an agent will have a consequent belief Q. Notably, the truth conditions for TSIMs include a subject-matter filter so that the topic of the consequent Q must be "included" within that of the antecedent. To extend the account to languages with richer expressivity thus requires an expanded account of subject-matter. In this talk, I will discuss extending earlier work on the subject-matter of intensional conditionals to the special case of modal sentences whose primary operators are interpreted by possible worlds semantics.



- - - - Tuesday, Nov 2, 2021 - - - -

Computational Logic Seminar
Tuesday November 2, 2021, 2-4pm Eastern Time US
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Stipe Pandzic, Utrecht University
Title: Non-monotonic reasoning and defeasible argumentation in justification logic

Abstract: In the 1980s, John Pollock’s work on defeasible reasons started the quest in the AI community for a formal system of defeasible argumentation. My goal in this talk is to present a logic of structured defeasible argumentation using the language of justification logic. One of the key features that is absent in standard justification logics is the possibility to weigh different epistemic reasons or pieces of evidence that might conflict with one another. To amend this, we develop a semantics for “defeaters”: conflicting reasons forming a basis to doubt the original conclusion or to believe an opposite statement.

Formally, non-monotonicity of reasons is introduced through default rules with justification logic formulas. The new logic manipulates defeasible justification assertions of the type t :F that read as “t is a defeasible reason that justifies F”. Such formulas are then interpreted as arguments and their acceptance semantics is given in analogy to Dung’s abstract argumentation framework semantics. In contrast to argumentation frameworks, however, determining arguments’ acceptance in default justification logic simply turns into finding (non-monotonic) logical consequences from a starting theory with justification assertions.

As one of the important results, we can show that a large subclass of Dung’s frameworks is a special case of default justification logic in the sense that (1) Dung’s frameworks can be obtained from justification logic-based theories by focusing on a single aspect of attacks among justification logic arguments (in analogy to “forgetful projection” for standard justification logic) and (2) Dung’s warranted frameworks always have multiple justification logic instantiations called “realizations”. By the end of the talk, I show how default justification logic unifies all three standard types of argumentative attack in AI, namely rebutting, undercutting and undermining attacks, as a first logic of this kind.




- - - - Wednesday, Nov 3, 2021 - - - -



- - - - Thursday, Nov 4, 2021 - - - -



- - - - Friday, Nov 5, 2021 - - - -

Philog Seminar
Friday, November 5, 2021, 10:30 AM
(Zoom link will be posted on https://philog.arthurpaulpedersen.org/)
Sonja Smets, University of Amsterdam
Title: Computing Social Behavior
 
Abstract:  Recently, epistemic-social phenomena have received more attention from the logic community, analyzing peer pressure, studying informational cascades, inspecting priority-based peer influence, modeling diffusion and prediction, and examining reflective social influence. In this presentation, I will contribute to this line of work and focus in particular on the logical features of social group creation. I pay attention to the mechanisms which indicate when agents can form a team based on the correspondence in their set of features (behavior, opinions, etc.). Our basic approach uses a semi-metric on the set of agents, which is used to construct a network topology. This structure is then extended with epistemic features to represent the agents' epistemic states, allowing us to explore group-creation alternatives where what matters is not only the agent's differences but also what they know about them. The logical settings in this work make use of the techniques of dynamic epistemic logic to represent group-creation actions, to define new languages in order to describe their effects, and to provide sound and complete axiom systems. This talk is based on joint work with Fernando Velazquez Quesada.

Sonja Smets is a Belgian and Dutch logician and epistemologist known for her work in belief revision and quantum logic. She is Professor of Logic and Epistemology at the University of Amsterdam, where she directed the university's Institute for Logic, Language and Computation and is affiliated with both the Faculty of Science and the Department of Philosophy.




Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.








Next Week in Logic at CUNY:

- - - - Monday, Nov 8, 2021 - - - -



- - - - Tuesday, Nov 9, 2021 - - - -



- - - - Wednesday, Nov 10, 2021 - - - -



- - - - Thursday, Nov 11, 2021 - - - -



- - - - Friday, Nov 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 12, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property II

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

The next session of the Barcelona Set Theory Semina will take place tomorrow: 

SPEAKER:   Sean Cox (Virginia Commonwealth University)
TITLE: Homological algebra, elementary submodels, and stationary logic
DATE: 3 November 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online via Zoom:


Announcement attached below.

Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Piotr Koszmider; An application of Schreier's family

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 2.11.2021, 13.30, room 105, Speaker: Piotr Koszmider (IMPAN) Title: "An application of Schreier's family" Abstact: "We will present the original solution due to J. Schreier of a problem of S. Banach which uses a subset of the Boolean algebra of clopen subsets of [0, ω^ω] induced by a family of finite subsets of ℕ known as Schreier's family". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

(KGRC) talk in the Logic Colloquium on Thursday, November 4

Kurt Godel Research Center
The KGRC welcomes as guests: Fortunato Maesano (host: Lyubomyr Zdomskyy) will visit the KGRC from November 1 to June 30, 2022. Jaroslav Šupina (host: Serhii Bardyla) will visit from November 2 to November 9. * * * Set Theory Research Seminar Please note that the Set Theory Research Seminar is at recess. The next talk has been scheduled for November 9. * * * Logic Colloquium Kurt Gödel Research Center Thursday, November 4 "How geometry became structural" Georg Schiemer (Universität Wien) Structuralism in the philosophy of mathematics is, roughly put, the view that mathematical theories study abstract structures or the structural properties of their subject fields. The position is strongly rooted in modern mathematical practice. In fact, one can understand structuralism as an attempt to come to terms philosophically with a number of wide-ranging methodological transformations in 19th and early 20th century mathematics, related to the rise of modern geometry, number theory, and abstract algebra. The present talk will focus on the geometrical roots of structuralism. Specifically, we will survey some of the key conceptual changes in geometry between 1860 and 1910 that eventually led to a “structural turn” in the field. This includes (i) the gradual implementation of model-theoretic techniques in geometrical reasoning, for instance, the focus on duality and transfer principles in projective geometry; (ii) the unification of geometrical theories by algebraic methods, specifically, by the use of transformation groups in Felix Klein’s Erlangen Program; and (iii) the successive consolidation of formal axiomatics in work by Hilbert and others. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the talk we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Logic Seminar Wed 3 Nov 2021 16:00 at NUS by Wu Guohua, NTU

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 3 November 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Wu Guohua Title: Domains: where Scott and Ershov met without appointment Abstract: Domain theory was contrived by Dana Scott in 1969 as a theory of approximating computations. This topic was also raised by Ershov independently. In this talk, I will give a brief introduction of domain theory first, hopefully, from the beginning, and then move to the comparison of various substitutions of Hausdorff property, including sobriety, well-filteredness and monotone convergence. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday November 3rd at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Paul Szeptycki -- An example from a square-sequence, convergence and the G_delta-topology. Questions of Bella concerning cardinal invariants of the G_delta topology and questions of Arhangel'skii on strong convergence properties are answered with examples constructed from square(kappa) sequences. Best, David

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

The next session of the Barcelona Set Theory Semina will take place tomorrow: 

SPEAKER:   Martina Iannella (Università degli Studi di Udine)
TITLE: Convex embeddability on linear/circular orders and connections to knot theory
DATE: 27 October 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:


Announcement attached below.

Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.



Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 25, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 25, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 

Noah Friedman-Biglin (San José State University)
Title: Regrounding the Unworldly: Pluralism and Politics in Carnap’s Philosophy of Logic

Abstract: The locus classicus of logical pluralism – that is, the view that there is more than on logic, properly so called – since the earliest days of analytic philosophy, can be found in Rudolf Carnap’s ‘principle of tolerance’. Clarifying the principle of tolerance is the focus of this first section of this paper. I will argue that the principle should be understood as widely as possible, and thus we will see that Carnap’s tolerance is a very radical view. In section two, I discuss the motivations Carnap had for his pluralism, and argue that they are based in the Vienna Circle’s “Scientific World-Conception” — a platform of philosophical commitments which set the direction for the Circle’s philosophical investigations as well as a program of social change. What emerges from this discussion is the often-ignored relationship between his logical pluralism and his political views. In short, I will argue that the radical quality of his tolerance is due to these political commitments. In section three, I examine the reasons why this connection is not very well-known. I will argue that the political situation in the United States in the aftermath of World War 2 created conditions where it was dangerous to explicitly link scholarly work and politics, and discuss the reasons that Carnap might have had for distancing himself from – or at least de-emphasizing – the political foundations of his views.




- - - - Tuesday, Oct 26, 2021 - - - -

Computational Logic seminar 
Graduate Center CUNY (online)
Tuesday October 26, 2021, 2-4p, Eastern Time US.
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Sergei Artemov, Graduate Center CUNY
Title:   On logical foundations of strategic games

Abstract:  In his dissertation of 1950, Nash based his concept of solution to a game on the principles that  "a rational prediction should be unique, that the players should be able to deduce and make use of it." Nash noticed that such a definitive solution is always a Nash Equilibrium (NE). We observe that, for the basic notion of Aumann's rationality, NE, even if it is unique, is not necessarily Nash's definitive solution.  We show that the Iterated Deletion of Strictly Dominated Strategies is a complete procedure for Nash's definitive solution for strategic games.





- - - - Wednesday, Oct 27, 2021 - - - -



- - - - Thursday, Oct 28, 2021 - - - -



- - - - Friday, Oct 29, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Kameryn Williams, Sam Houston State University
Potentialism about classes





Next Week in Logic at CUNY:

- - - - Monday, Nov 1, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Monday, October 25th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Fedor Pakhomov Ghent University

This is a joint work with Albert Visser. We prove that no consistent finitely axiomatized theory one-dimensionally interprets its own extension with predicative comprehension. This constitutes a result with the flavor of the Second Incompleteness Theorem whose formulation is completely arithmetic-free. Probably the most important novel feature that distinguishes our result from the previous results of this kind is that it is applicable to arbitrary weak theories, rather than to extensions of some base theory. The methods used in the proof of the main result yield a new perspective on the notion of sequential theory, in the setting of forcing-interpretations. https://arxiv.org/abs/2109.02548 




Logic and Metaphysics Workshop
Date: Monday, November 1, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 
Thomans M Ferguson (Amsterdam)
The Subject-Matter of Modal Sentences

The framework of topic-sensitive intentional modal operators (TSIMs) described by Berto provides a general platform for representing agents' intentional states of various kinds. For example, a TSIM can model doxastic states, capturing a notion that given the acceptance of antecedent information P, an agent will have a consequent belief Q. Notably, the truth conditions for TSIMs include a subject-matter filter so that the topic of the consequent Q must be "included" within that of the antecedent. To extend the account to languages with richer expressivity thus requires an expanded account of subject-matter. In this talk, I will discuss extending earlier work on the subject-matter of intensional conditionals to the special case of modal sentences whose primary operators are interpreted by possible worlds semantics.



- - - - Tuesday, Nov 2, 2021 - - - -



- - - - Wednesday, Nov 3, 2021 - - - -



- - - - Thursday, Nov 4, 2021 - - - -



- - - - Friday, Nov 5, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, November 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Tom Benhamou, Tel Aviv University
Intermediate Prikry-type models, quotients, and the Galvin property

We classify intermediate models of Magidor-Radin generic extensions. It turns out that similar to Gitik Kanovei and Koepke's result, every such intermediate model is of the form  where  is a subsequence of the generic club added by the forcing. The proof uses the Galvin property for normal filters to prove that quotients of some Prikry-type forcings are -c.c. in the generic extension and therefore do not add fresh subsets to . If time permits, we will also present results regarding intermediate models of the Tree-Prikry forcing.





- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Damian Głodkowski; The poset of projections in the Calkin algebra, cont.

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 26.10.2021, 13.30, room 105, Speaker: Damian Głodkowski (IMPAN/MIM UW) Title: "The poset of projections in the Calkin algebra" continuation Abstact: "We will discuss the set-theoretic properties of the poset of projections in the Calkin algebra of the separable Hilbert space, taking into account possible types of maximal well-ordered sequences and maximal antichains. We will show that it is consistent that among the mentioned subsets there are some with cardinality less than continuum and that Martin's axiom implies that all of them have cardinality continuum. We will also discuss relations between the poset of projections and the Boolean algebra P(ω)/Fin. Based on: Wofsey, Eric; P(ω)/fin and projections in the Calkin algebra. Proc. Amer. Math. Soc. 136 (2008), no. 2, 719-726. ". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Next CMU math logic seminar (special time)

Carnegie Mellon Logic Seminar
TUESDAY, October 26, 2021 Mathematical logic seminar: 4:30 PM (Eastern), Online, Jason Parker, Brandon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Polymorphic automorphisms and the Picard group ABSTRACT: We investigate the concept of definable, or inner, automorphism in the logical setting of partial Horn theories. The central technical result extends a syntactical characterization of the group of such automorphisms (called the covariant isotropy group) associated with an algebraic theory to the wider class of quasi-equational theories. We apply this characterization to prove that the isotropy group of a strict monoidal category is precisely its Picard group of invertible objects. Furthermore, we obtain an explicit description of the covariant isotropy group of a presheaf category.

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar next week (Wednesday October 27th). People are instead advised to participate the Workshop on Generic Structures which takes place in the Institute next week. https://gens.math.cas.cz/ A leaked preliminary schedule of the workshop for Wednesday October 27 (Yugoslav session): 9:00--9:45 Mirna Džamonja: Morass-generic structures 9:45--10:30 Boriša Kuzeljević: Tukey order of directed sets of cofinality ω2 11:15--12:00 Stevo Todorčević: Ramsey degrees of the topological Q 14:15--15:00 Paul Szeptycki: A topological space from a square(κ) sequence related to convergence and cardinal invariants of the Gδ topology Best, David

Logic Seminar Wed 27 Oct 2021 17:00 hrs at NUS by Mars Yamaleev

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 27 October 2021, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Mars Yamaleev, Kazan Federal University Title: On the Shoare-Stob Theorem URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: In our talk we consider relative enumerability of 2-c.e. Turing degrees in c.e. degrees below them. We focus on an old question which arises from the well-known work of Soare and Stob in 1982. The Soare-Stob theorem says that for any noncomputable low c.e. Turing degree a there exists a non-c.e. Turing degree d which is above a and relative enumerable in a. The question is whether the degree d can always be chosen as 2-c.e. We answer this question by showing that for some a the degree d must be beyond 2-c.e., and discuss the ideas of proof. Also we consider possible generalizations of this result. All results are obtained in a joint work with Arslanov M.M. and Batyrshin I.I.

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Please note that Friday's Logic Workshop will use the same zoom link usually used for the Set Theory Seminar. For details about obtaining it, see nylogic.github.io 

Best,
Jonas

This Week in Logic at CUNY:

- - - - Wednesday, Oct 20, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Dan Shiebler, Oxford University.
Date and Time:     Wednesday October 20, 2021, 7:00 - 8:30 PM., on Zoom.
Title:     Out of Sample Generalization with Kan Extensions.

Abstract: A common problem in data science is use this function defined over this small set to generate predictions over that larger set. Extrapolation, interpolation, statistical inference and forecasting all reduce to this problem. The Kan extension is a powerful tool in category theory that generalizes this notion. In this work we explore several applications of Kan extensions to data science.



- - - - Thursday, Oct 21, 2021 - - - -



- - - - Friday, Oct 22, 2021 - - - -

Logic Workshop
CUNY Graduate Center
Friday, October 22, 2:00-3:30pm
The seminar will take place virtually at 2:00pm US Eastern Standard Time. The zoom link is the same one usually used for the Set Theory Seminar. For details about obtaining it, see nylogic.github.io 
Matthias Aschenbrenner, University of Vienna
The elementary theory of maximal Hardy fields

A Hardy field is a differential field of germs at infinity of one-variable differentiable real-valued functions defined on half-lines. Hardy fields appear naturally in model theory and its applications to real analytic geometry and dynamical systems, and also have found uses in computer algebra, ergodic theory, and various other fields of mathematics. I will discuss some optimal extension results for Hardy fields obtained in the last few years, which lead to a description of the theory of maximal Hardy fields and applications to ordinary differential equations. (This is joint work with Lou van den Dries and Joris van der Hoeven.)





Next Week in Logic at CUNY:

- - - - Monday, Oct 25, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 25, 4.15-6.15 (NY time)
For meeting information, please sign up for our mailing list at https://logic.commons.gc.cuny.edu/about/ 

Noah Friedman-Biglin (San José State University)
Title: Regrounding the Unworldly: Pluralism and Politics in Carnap’s Philosophy of Logic

Abstract: The locus classicus of logical pluralism – that is, the view that there is more than on logic, properly so called – since the earliest days of analytic philosophy, can be found in Rudolf Carnap’s ‘principle of tolerance’. Clarifying the principle of tolerance is the focus of this first section of this paper. I will argue that the principle should be understood as widely as possible, and thus we will see that Carnap’s tolerance is a very radical view. In section two, I discuss the motivations Carnap had for his pluralism, and argue that they are based in the Vienna Circle’s “Scientific World-Conception” — a platform of philosophical commitments which set the direction for the Circle’s philosophical investigations as well as a program of social change. What emerges from this discussion is the often-ignored relationship between his logical pluralism and his political views. In short, I will argue that the radical quality of his tolerance is due to these political commitments. In section three, I examine the reasons why this connection is not very well-known. I will argue that the political situation in the United States in the aftermath of World War 2 created conditions where it was dangerous to explicitly link scholarly work and politics, and discuss the reasons that Carnap might have had for distancing himself from – or at least de-emphasizing – the political foundations of his views.


Models of Peano Arithmetic (MOPA)
Monday, October 25th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Fedor Pakhomov Ghent University


- - - - Tuesday, Oct 26, 2021 - - - -


- - - - Wednesday, Oct 27, 2021 - - - -



- - - - Thursday, Oct 28, 2021 - - - -



- - - - Friday, Oct 29, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Kameryn Williams, Sam Houston State University
Potentialism about classes




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 18, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 18, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Rohit Parikh (CUNY GC).
Title: States of Knowledge

Abstract: We know from long ago that among a group of people and given a true proposition P, various states of knowledge of P are possible. The lowest is when no one knows P and the highest is when P is common knowledge. The notion of common knowledge is usually attributed to David Lewis, but it was independently discovered by Schiffer. There are indications of it also in the doctoral dissertation of Robert Nozick. Aumann in his celebrated Agreeing to Disagree paper is generally thought to be the person to introduce it into game theory. But what are the intermediate states? It was shown by Pawel Krasucki and myself that there are only countably many and they correspond to what S. C. Kleene called regular sets. But different states of knowledge can cause different group actions. If you prefer restaurant A to B and so do I, and it is common knowledge, and we want to eat together, then we are likely to both go to A. But without that knowledge we might end up in B, or one in A and one in B. This was discussed by Thomas Schelling who also popularized the notion of focal points. Do different states of knowledge always lead to different group actions? Or can there be distinct states which cannot be distinguished through action? The question seems open. It obviously arises when we try to infer the states of knowledge of animals by witnessing their actions. We will discuss the old developments as well as some more recent ideas.



- - - - Tuesday, Oct 19, 2021 - - - -



- - - - Wednesday, Oct 20, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Dan Shiebler, Oxford University.
Date and Time:     Wednesday October 20, 2021, 7:00 - 8:30 PM., on Zoom.
Title:     Out of Sample Generalization with Kan Extensions.

Abstract: A common problem in data science is use this function defined over this small set to generate predictions over that larger set. Extrapolation, interpolation, statistical inference and forecasting all reduce to this problem. The Kan extension is a powerful tool in category theory that generalizes this notion. In this work we explore several applications of Kan extensions to data science.



- - - - Thursday, Oct 21, 2021 - - - -



- - - - Friday, Oct 22, 2021 - - - -

Logic Workshop
CUNY Graduate Center
Friday, October 22, 2:00-3:30pm
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.orgfor meeting id.
Matthias Aschenbrenner, University of Vienna
The elementary theory of maximal Hardy fields

A Hardy field is a differential field of germs at infinity of one-variable differentiable real-valued functions defined on half-lines. Hardy fields appear naturally in model theory and its applications to real analytic geometry and dynamical systems, and also have found uses in computer algebra, ergodic theory, and various other fields of mathematics. I will discuss some optimal extension results for Hardy fields obtained in the last few years, which lead to a description of the theory of maximal Hardy fields and applications to ordinary differential equations. (This is joint work with Lou van den Dries and Joris van der Hoeven.)





Next Week in Logic at CUNY:

- - - - Monday, Oct 25, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 25, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Noah Friedman-Biglin (San José State University)
Title: Regrounding the Unworldly: Pluralism and Politics in Carnap’s Philosophy of Logic

Abstract: The locus classicus of logical pluralism – that is, the view that there is more than on logic, properly so called – since the earliest days of analytic philosophy, can be found in Rudolf Carnap’s ‘principle of tolerance’. Clarifying the principle of tolerance is the focus of this first section of this paper. I will argue that the principle should be understood as widely as possible, and thus we will see that Carnap’s tolerance is a very radical view. In section two, I discuss the motivations Carnap had for his pluralism, and argue that they are based in the Vienna Circle’s “Scientific World-Conception” — a platform of philosophical commitments which set the direction for the Circle’s philosophical investigations as well as a program of social change. What emerges from this discussion is the often-ignored relationship between his logical pluralism and his political views. In short, I will argue that the radical quality of his tolerance is due to these political commitments. In section three, I examine the reasons why this connection is not very well-known. I will argue that the political situation in the United States in the aftermath of World War 2 created conditions where it was dangerous to explicitly link scholarly work and politics, and discuss the reasons that Carnap might have had for distancing himself from – or at least de-emphasizing – the political foundations of his views.


Models of Peano Arithmetic (MOPA)
Monday, October 25th, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Fedor Pakhomov Ghent University


- - - - Tuesday, Oct 26, 2021 - - - -


- - - - Wednesday, Oct 27, 2021 - - - -



- - - - Thursday, Oct 28, 2021 - - - -



- - - - Friday, Oct 29, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Kameryn Williams, Sam Houston State University
Potentialism about classes




- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Philip Welch (University of Bristol)
TITLE: The universe constructed from a set (or class) of regular cardinals
DATE: 20 October 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:



Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Damian Głodkowski; The poset of projections in the Calkin algebra

IMPAN Working Group in Applications of Set Theory
Seminar: Working group in applications of set theory, IMPAN Tuesday, 19.10.2021, 13.30, room 105, Speaker: Damian Głodkowski (IMPAN/MIM UW) Title: "The poset of projections in the Calkin algebra" Abstact: "We will discuss the set-theoretic properties of the poset of projections in the Calkin algebra of the separable Hilbert space, taking into account possible types of maximal well-ordered sequences and maximal antichains. We will show that it is consistent that among the mentioned subsets there are some with cardinality less than continuum and that Martin's axiom implies that all of them have cardinality continuum. We will also discuss relations between the poset of projections and the Boolean algebra P(ω)/Fin. Based on: Wofsey, Eric; P(ω)/fin and projections in the Calkin algebra. Proc. Amer. Math. Soc. 136 (2008), no. 2, 719-726. ". Visit our seminar page which may include some future talks at https://www.impan.pl/~set_theory/Seminar/

Logic Seminar Wed 20 Oct 2021 16:00 hrs at NUS by Yang Yue

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 20 Oct 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Yang Yue, NUS Title: A recursive coloring without Delta-3 solutions for Hindman's Theorem URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: This is a follow up of Liao Yuke's talk last week. I will explain in detail his result which says that there exists a recursive coloring f: N -> {0,1} such that for all infinite subset X of N, if FS(X) is homogeneous for f, then X is not recursive in 0''. Here FS(X) is the set of all finite sums of distinct elements of X. Liao Yuke's result improved Blass, Hirst and Simpson's theorem in 1987 (from no 0' recursive solutions to no 0'' recursive ones).

(KGRC) seminar talks on Tuesday, October 19 and Thursday, October 21

Kurt Godel Research Center
The KGRC welcomes as guest: Chris Lambie-Hanson (host: Vera Fischer) will visit from October 18 to October 23 and give two talks (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, October 19 "Strongly unbounded subadditive colorings" Chris Lambie-Hanson (Czech Academy of Sciences) Given infinite cardinals $\kappa$ and $\theta$, functions of the form $c:[\kappa]^2 \rightarrow \theta$ exhibiting certain unboundedness properties provide a strong counterexample to the generalization of Ramsey's theorem to $\kappa$ and have seen a wide variety of applications. In this talk, we will discuss the existence of such strongly unbounded colorings, focusing in particular on colorings with subadditivity properties. We will then present some applications to general topology. In particular, building on work of Chen-Mertens and Szeptycki, we will prove that the failure of the Singular Cardinals Hypothesis implies the existence of a Fr\'{e}chet, $\alpha_1$-space whose $G_\delta$-modification has large tightness. This is joint work with Assaf Rinot. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the talk we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! * * * Logic Colloquium Kurt Gödel Research Center Thursday, October 21 "Variations on a theorem of Silver" Chris Lambie-Hanson (Czech Academy of Sciences) Shortly after the advent of forcing in the 1960s, Easton proved that, modulo some trivial constraints concerning monotonicity and cofinality, the axioms of set theory place no restrictions on the behavior of exponentiation at regular cardinals. In a surprising turn of events, this turned out not to be the case for singular cardinals, and the last half-century has seen a procession of deep results uncovering nontrivial constraints on exponentiation at singular cardinals. One of the first of these results was Silver's theorem, which in essence states that if $\lambda$ is a singular cardinal of uncountable cofinality and there are "many" singular cardinals $\kappa < \lambda$ such that $2^\kappa = \kappa^+$, then it must also be the case that $2^\lambda = \lambda^+$. In particular, if the Singular Cardinals Hypothesis fails, then it must fail first at a singular cardinal of countable cofinality. We will discuss this seminal theorem and a number of variations thereon, and we will end by sketching a proof of a version of Silver's theorem pertaining to certain generalized cardinal characteristics. Time and Place Talk at 3:00pm, mixed mode (in person as well as via Zoom) Universität Wien Institut für Mathematik Lecture Hall HS 13 2nd floor Oskar-Morgenstern-Platz 1 1090 Wien If you want to attend in person, please be aware of the fact that you will be required to show proof of your COVID-19 "2.5G" status (vaccinated, recovered, PCR tested) upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the talk we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.) Zoom: This talk will be given in person as well as via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Talks next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, October 19, 2021 Mathematical logic seminar: 3:30 P.M., Online, Andreas Blass, University of Michigan Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Tukey Ordering and Forcing Preservation of Ultrafilters, part 1 ABSTRACT: I plan to describe two species of ultrafilters on the set of natural numbers and to speculate about a connection between them. For both species, the central question is whether ZFC can prove the existence of such ultrafilters. One species is defined in terms of the Tukey ordering of directed sets, but it also admits a more combinatorial definition. The other species is defined in terms of preservation by forcing, but it also admits a combinatorial definition. The two combinatorial definitions, though different, have very similar "flavor", and that leads to my speculations. I'll present the original definitions as well as the combinatorial equivalents, and then I'll discuss attempts to combine the key properties of the two species. TUESDAY, October 19, 2021 Set Theory Reading Group: 4:30 P.M., Online, Andreas Blass, University of Michigan Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Tukey Ordering and Forcing Preservation of Ultrafilters, part 2 ABSTRACT: I plan to describe two species of ultrafilters on the set of natural numbers and to speculate about a connection between them. For both species, the central question is whether ZFC can prove the existence of such ultrafilters. One species is defined in terms of the Tukey ordering of directed sets, but it also admits a more combinatorial definition. The other species is defined in terms of preservation by forcing, but it also admits a combinatorial definition. The two combinatorial definitions, though different, have very similar "flavor", and that leads to my speculations. I'll present the original definitions as well as the combinatorial equivalents, and then I'll discuss attempts to combine the key properties of the two species.

Wednesday seminar

Prague Set Theory Seminar
Dear all, There is no seminar tomorrow Wednesday October 13th. The seminar meets again next week on Wednesday October 20th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Noé de Rancourt -- A nonseparable version of Pełczyński's unconditional space, part 2 Abstract: Pełczyński's unconditional space is a well-known example of a separable Banach space having a universal unconditional basis. It can be seen as a Fraïssé limit, and in particular, it has many nontrivial isometries. In a common work in progress with Ziemowit Kostana, we built a nonseparable version of this space in a forcing extension. Surprisingly, unlike its separable counterpart, our space is very rigid. In my last talk, I presented the motivations of this construction and the required preliminaries in Banach space theory. In this second talk, I will concentrate on the actual construction, and the proof of the rigidity properties, namely: - every operator on our space is the sum of a diagonal operator and an operator with separable range; - all onto isometries of our space are trivial. As the first talk was mainly classical preliminaries, this talk will be accessible to those of you who know the basics of Banach space theory (actually, the theory of unconditional bases), even if they haven't attended the first talk. Best, David

Logic Seminar Wednesday 13 October 2021 16:00 hrs at NUS by Liao Yuke

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 13 October 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Liao Yuke Title: Computable coloring without Pi-3 solution for Hindman's Theorem URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Hindman's theorem is a Ramsey type theorem related to finite sum while its proof-theoretic strength still has a huge gap. One form of the question is that if any computable coloring function would have an arithmetic solution (homogeneous set). We will construct a computable coloring functions that no Pi-3 set can be homogeneous.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 11, 2021 - - - -

*** GRAD CENTER CLOSED TODAY ***



- - - - Tuesday, Oct 12, 2021 - - - -

Computational Logic Seminar
Tuesday October 12, 2021, 2-4pm
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speakers: 
Rui-Jie Yew, Massachusetts Institute of Technology
Pavel Naumov, University of Southampton, UK
Title: Three Forms of Responsibility in Multiagent Systems

Abstract:  In this talk we define and discuss three distinct forms of responsibility in multiagent systems that have been previously considered in the literature: counterfactual responsibility, responsibility for seeing-to-it, and responsibility for forcing. We show that, in the case of the extensive form games, none of these forms can be defined through the other two. In strategic games, the responsibility for seeing-to-it and the responsibility for forcing are equivalent, and their expressibility through the counterfactual responsibility depends on the technical details of the language and the semantics. Finally, we observe that the ownership and the accountability of one agent for another lead to forms of responsibility different from the three that we studied. 

- - - - Wednesday, Oct 13, 2021 - - - -



- - - - Thursday, Oct 14, 2021 - - - -



- - - - Friday, Oct 15, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 1
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Yuxin Zhou University of Florida

Let  be a natural number, let  be the hypergraph of isosceles triangles in . Under the axiom of choice, the existence of a countable coloring for  is true for every . Without the axiom of choice, the coloring problems will be hard to answer. We often expect the case that the countable chromatic number of one hypergraph doesn't imply the one for another. With an inaccessible cardinal, there is a model of ZF+DC in which  has countable chromatic number while  has uncountable chromatic number. This result is obtained by a balanced forcing over the symmetric Solovay model.





Next Week in Logic at CUNY:

- - - - Monday, Oct 18, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 4, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Rohit Parikh (CUNY GC).
Title: States of Knowledge

Abstract: We know from long ago that among a group of people and given a true proposition P, various states of knowledge of P are possible. The lowest is when no one knows P and the highest is when P is common knowledge. The notion of common knowledge is usually attributed to David Lewis, but it was independently discovered by Schiffer. There are indications of it also in the doctoral dissertation of Robert Nozick. Aumann in his celebrated Agreeing to Disagree paper is generally thought to be the person to introduce it into game theory. But what are the intermediate states? It was shown by Pawel Krasucki and myself that there are only countably many and they correspond to what S. C. Kleene called regular sets. But different states of knowledge can cause different group actions. If you prefer restaurant A to B and so do I, and it is common knowledge, and we want to eat together, then we are likely to both go to A. But without that knowledge we might end up in B, or one in A and one in B. This was discussed by Thomas Schelling who also popularized the notion of focal points. Do different states of knowledge always lead to different group actions? Or can there be distinct states which cannot be distinguished through action? The question seems open. It obviously arises when we try to infer the states of knowledge of animals by witnessing their actions. We will discuss the old developments as well as some more recent ideas.



- - - - Tuesday, Oct 19, 2021 - - - -



- - - - Wednesday, Oct 20, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Dan Shiebler, Oxford University.
Date and Time:     Wednesday October 20, 2021, 7:00 - 8:30 PM., on Zoom.
Title:     Out of Sample Generalization with Kan Extensions.

Abstract: A common problem in data science is use this function defined over this small set to generate predictions over that larger set. Extrapolation, interpolation, statistical inference and forecasting all reduce to this problem. The Kan extension is a powerful tool in category theory that generalizes this notion. In this work we explore several applications of Kan extensions to data science.



- - - - Thursday, Oct 21, 2021 - - - -



- - - - Friday, Oct 22, 2021 - - - -

Logic Workshop
CUNY Graduate Center
Friday, October 22, 2:00-3:30pm
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Matthias Aschenbrenner, University of Vienna



- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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UPDATE - This Week in Logic at CUNY

This Week in Logic at CUNY
Note the addition of Thursday's talk by Yuri Gurevich in the Philog Seminar.

Best,
Jonas


This Week in Logic at CUNY:


- - - - Monday, Oct 4, 2021 - - - -

Penn Logic and Computation Seminar
Monday, October 4, 3:30 pm US Eastern, online
Speaker: Sergei Artemov, CUNY Graduate Center
Title: Missing Proofs and the Provability of Consistency

Abstract: We argue that there is a class of widely used and readily formalizable arithmetical proofs of universal properties which are not accounted for in the traditional unprovability of consistency analysis. On this basis, we offer a mathematical proof of consistency for Peano Arithmetic PA and demonstrate that this proof is formalizable in PA. This refutes the widespread belief that there exists no consistency proof of a system that can be formalized in the system itself. Gödel’s Second Incompleteness theorem yields that PA cannot derive the consistency formula ConPA. This does not interfere with our formalized proof of PA-consistency which is not a derivation of the consistency formula ConPA.

The link will be available by 12 noon on Monday. To get it, contact Andre Scedrov <scedrov@math.upenn.edu> or Sergei Artemov <sartemov@gc.cuny.edu>.



Logic and Metaphysics Workshop
Date: Monday, October 4, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Speaker: Yale Weiss (CUNY GC)
Title: Bisemilattice Semantics for Intuitionistic and Relevant Modal Logics

Abstract: In this talk, I consider modal logics extending J (intuitionistic logic) and RMO (sometimes called ‘constructive mingle’). Adapting previous work of Humberstone, all of these systems are given a purely operational bisemilattice semantics and soundness and completeness results are proved. I consider a way of exactly translating each intuitionistic modal system into a relevant modal companion and discuss what, if any, light this sheds on the interpretation of the relevant companions. Various applications are examined (e.g., to developing constructive theories of entailment) and results germane to those applications are proved. I also discuss connections between the present semantic framework and related frameworks, including Fine’s hybrid operational-partial order semantics, inquisitive semantics, and Urquhart’s semilattice semantics.



- - - - Tuesday, Oct 5, 2021 - - - -

Computational Logic Seminar
Tuesday October 5, 2021, 2-4pm
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Noson Yanofsky, CUNY
Title: Diagonalization, Fixed Points, and Self-reference

Abstract: Some of the most profound and famous theorems in mathematics and computer science of the past 150 years can simultaneously be seen as a consequence of diagonalization, as a fixed-point theorem, and as an instance of a self-referential paradox. These results include Cantor's theorems about different levels of infinity; Russell's paradox; Gödel's incompleteness theorem; Turing's halting problem; and much more. Amazingly, all these diverse theorems and all viewpoints can be seen as instances of a single simple theorem of basic category theory. We describe this theorem and show some of the instances. A large part of the talk will be a discussion of diagonalization proofs and fixed point theorems that fail to be instances of this categorical theorem. We will meet another categorical idea that unifies some of those instances. No category theory is needed for this talk.




- - - - Wednesday, Oct 6, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Gemma De las Cuevas, University of Innsbruck.
Date and Time:     Wednesday October 6, 2021, 7:00 - 8:30 PM., on Zoom.
Title:     From simplicity to universality and undecidability.

Abstract: Why is it so easy to generate complexity? I will suggest that this is due to the phenomenon of universality — essentially every non-trivial system is universal, and thus able to explore all complexity in its domain. We understand universality in spin models, automata and neural networks. I will present the first step toward rigorously linking the first two, where we cast classical spin Hamiltonians as formal languages and classify the latter in the Chomsky hierarchy. We prove that the language of (effectively) zero-dimensional spin Hamiltonians is regular, one-dimensional spin Hamiltonians is deterministic context-free, and higher-dimensional and all-to-all spin Hamiltonians is context-sensitive. I will also talk about the other side of the coin of universality, namely undecidability, and will raise the question of whether universality is visible in Lawvere’s Theorem.


- - - - Thursday, Oct 7, 2021 - - - -

Philog Seminar
Thursday, October 7, 6:30 PM
A Zoom link will be posted  Wednesday on https://philog.arthurpaulpedersen.org/
Negative probabilities: What are they for?
Yuri Gurevich, University of Michigan

The topic may sound nonsensical. The standard frequential interpretation of probabilities makes no sense for negative probabilities. Yet negative probabilities are profitably used in quantum physics and elsewhere. So what are they? What is their intrinsic meaning? We don't know. There are attempts in the literature to provide meaning for negative probabilities but, in our judgement, the problem is wide open.

Instead, we address a more pragmatic question: What are negative probabilities good for? It is not rare in science to use a concept without understanding its intrinsic meaning. Consider early uses of complex numbers. The standard quantitative interpretation of numbers makes no sense for imaginary numbers. And the intrinsic meaning of imaginary numbers wasn't clear (and is debatable even today). Yet complex numbers were profitably used to solve algebraic equations. It turned out, for example, that many real algebraic numbers cannot be
expressed in radicals unless we allow non-real complex coefficients.

It turns out that the disparate quantum applications of negative probabilities can be seen as examples of a certain application template. To make this template explicit, we introduce observation spaces. An observation space S is a family of (nonnegative) probability distributions P1, P2, ... on a common sample space. A question arises whether there is a single probability distribution P (a grounding for S) which yields all P1, P2, ... as marginal distributions. That P may be necessarily signed. We solve the grounding problem for a number of observation spaces of note.

The talk is based on a recent paper with Andreas Blass in J. Phys. A.



- - - - Friday, Oct 8, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 8
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Brent Cody, Virginia Commonwealth University
Higher derived topologies
By beginning with the order topology on an ordinal , and iteratively declaring more and more derived sets to be open, Bagaria defined the derived topologies  on , where  is an ordinal. He showed that the non-isolated points in the space  can be characterized using a strong form of iterated simultaneous stationary reflection called -s-reflection, which is deeply connected to certain transfinite indescribability properties. However, Bagaria's definitions break for  because, under his definitions, the -th derived topology  is discrete and no ordinal  can be -s-stationary. We will discuss some new work in which we use certain diagonal versions of Bagaria's definitions to extend his results. For example, we introduce the notions of diagonal Cantor derivative and use it to obtain a sequence of derived topologies on a regular  that is strictly longer than that of Bagaria's, under certain hypotheses.



Next Week in Logic at CUNY:

- - - - Monday, Oct 11, 2021 - - - -



- - - - Tuesday, Oct 12, 2021 - - - -



- - - - Wednesday, Oct 13, 2021 - - - -



- - - - Thursday, Oct 14, 2021 - - - -



- - - - Friday, Oct 15, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 1
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Yuxin Zhou University of Florida


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Oct 4, 2021 - - - -

Penn Logic and Computation Seminar
Monday, October 4, 3:30 pm US Eastern, online
Speaker: Sergei Artemov, CUNY Graduate Center
Title: Missing Proofs and the Provability of Consistency

Abstract: We argue that there is a class of widely used and readily formalizable arithmetical proofs of universal properties which are not accounted for in the traditional unprovability of consistency analysis. On this basis, we offer a mathematical proof of consistency for Peano Arithmetic PA and demonstrate that this proof is formalizable in PA. This refutes the widespread belief that there exists no consistency proof of a system that can be formalized in the system itself. Gödel’s Second Incompleteness theorem yields that PA cannot derive the consistency formula ConPA. This does not interfere with our formalized proof of PA-consistency which is not a derivation of the consistency formula ConPA.

The link will be available by 12 noon on Monday. To get it, contact Andre Scedrov <scedrov@math.upenn.edu> or Sergei Artemov <sartemov@gc.cuny.edu>.



Logic and Metaphysics Workshop
Date: Monday, October 4, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Speaker: Yale Weiss (CUNY GC)
Title: Bisemilattice Semantics for Intuitionistic and Relevant Modal Logics

Abstract: In this talk, I consider modal logics extending J (intuitionistic logic) and RMO (sometimes called ‘constructive mingle’). Adapting previous work of Humberstone, all of these systems are given a purely operational bisemilattice semantics and soundness and completeness results are proved. I consider a way of exactly translating each intuitionistic modal system into a relevant modal companion and discuss what, if any, light this sheds on the interpretation of the relevant companions. Various applications are examined (e.g., to developing constructive theories of entailment) and results germane to those applications are proved. I also discuss connections between the present semantic framework and related frameworks, including Fine’s hybrid operational-partial order semantics, inquisitive semantics, and Urquhart’s semilattice semantics.



- - - - Tuesday, Oct 5, 2021 - - - -

Computational Logic Seminar
Tuesday October 5, 2021, 2-4pm
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Noson Yanofsky, CUNY
Title: Diagonalization, Fixed Points, and Self-reference

Abstract: Some of the most profound and famous theorems in mathematics and computer science of the past 150 years can simultaneously be seen as a consequence of diagonalization, as a fixed-point theorem, and as an instance of a self-referential paradox. These results include Cantor's theorems about different levels of infinity; Russell's paradox; Gödel's incompleteness theorem; Turing's halting problem; and much more. Amazingly, all these diverse theorems and all viewpoints can be seen as instances of a single simple theorem of basic category theory. We describe this theorem and show some of the instances. A large part of the talk will be a discussion of diagonalization proofs and fixed point theorems that fail to be instances of this categorical theorem. We will meet another categorical idea that unifies some of those instances. No category theory is needed for this talk.




- - - - Wednesday, Oct 6, 2021 - - - -

The New York City Category Theory Seminar
Department of Computer Science
Department of Mathematics
The Graduate Center of The City University of New York
New URL:  http://www.sci.brooklyn.cuny.edu/~noson/Seminar/index.html
Contact N Yanofsky for zoom info (noson@sci.brooklyn.cuny.edu)
Speaker:     Gemma De las Cuevas, University of Innsbruck.
Date and Time:     Wednesday October 6, 2021, 7:00 - 8:30 PM., on Zoom.
Title:     From simplicity to universality and undecidability.

Abstract: Why is it so easy to generate complexity? I will suggest that this is due to the phenomenon of universality — essentially every non-trivial system is universal, and thus able to explore all complexity in its domain. We understand universality in spin models, automata and neural networks. I will present the first step toward rigorously linking the first two, where we cast classical spin Hamiltonians as formal languages and classify the latter in the Chomsky hierarchy. We prove that the language of (effectively) zero-dimensional spin Hamiltonians is regular, one-dimensional spin Hamiltonians is deterministic context-free, and higher-dimensional and all-to-all spin Hamiltonians is context-sensitive. I will also talk about the other side of the coin of universality, namely undecidability, and will raise the question of whether universality is visible in Lawvere’s Theorem.


- - - - Thursday, Oct 7, 2021 - - - -



- - - - Friday, Oct 8, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 8
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Brent Cody, Virginia Commonwealth University
Higher derived topologies
By beginning with the order topology on an ordinal , and iteratively declaring more and more derived sets to be open, Bagaria defined the derived topologies  on , where  is an ordinal. He showed that the non-isolated points in the space  can be characterized using a strong form of iterated simultaneous stationary reflection called -s-reflection, which is deeply connected to certain transfinite indescribability properties. However, Bagaria's definitions break for  because, under his definitions, the -th derived topology  is discrete and no ordinal  can be -s-stationary. We will discuss some new work in which we use certain diagonal versions of Bagaria's definitions to extend his results. For example, we introduce the notions of diagonal Cantor derivative and use it to obtain a sequence of derived topologies on a regular  that is strictly longer than that of Bagaria's, under certain hypotheses.



Next Week in Logic at CUNY:

- - - - Monday, Oct 11, 2021 - - - -



- - - - Tuesday, Oct 12, 2021 - - - -



- - - - Wednesday, Oct 13, 2021 - - - -



- - - - Thursday, Oct 14, 2021 - - - -



- - - - Friday, Oct 15, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 1
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Yuxin Zhou University of Florida


- - - - Other Logic News - - - -



- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

(KGRC) Set Theory Research Seminar talk on Tuesday, October 5

Kurt Godel Research Center
The KGRC welcomes as guest: Vladimir Tkachuk (host: Vera Fischer) will visit from October 3 to October 6 and give a talk (see below). * * * Set Theory Research Seminar Kurt Gödel Research Center Tuesday, October 5 "Exponential domination and its bidual in function spaces" Vladimir Tkachuk (Universidad Autonoma Metropolitana, Mexico City, Mexico) Given an infinite cardinal \kappa, we say that a space X features exponential \kappa-domination if every set A \subset X with |A| \leq 2^\kappa is contained in the closure of a set of cardinality \leq \kappa. Evidently, every space X of density not exceeding \kappa features exponential \kappa-domination. We will show that spaces with exponential \kappa-domination constitute a class with nice categorical properties and, in Cech-complete spaces, exponential \kappa-domination coincides with density \leq \kappa. Another merit of exponential \kappa-domination is that it has a bidual in function spaces. To show this, we will introduce exponential \kappa-cofinality and prove that X is exponentially \kappa-cofinal if and only if Cp(X) features exponential \kappa-domination and X is a space with exponential \kappa-domination if and only if Cp(X) is exponentially \kappa-cofinal. Time and Place Talk at 3:00pm, in person Universität Wien Institut für Mathematik Lecture Hall HS 8 1st floor Oskar-Morgenstern-Platz 1 1090 Wien Please be aware of the fact that you may be required to show proof of your 3G status upon entry of the buildings, or during sporadic random checks in the seminar rooms. During the Logic Colloquium we will also pass around an attendance sheet to facilitate contact tracing. (According to the regulations, this form will be kept for 28 days and destroyed thereafter.)

Two events on October 5

Carnegie Mellon Logic Seminar
TUESDAY, October 5, 2021 Mathematical logic seminar: 3:30 P.M., Online, Jindra Zapletal, University of Florida Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Set theory of algebraic hypergraphs ABSTRACT: I explain the main aim of the geometric set theory program: obtaining a careful calibration of Sigma two one sentences (typically, consequences of the axiom of choice) in choiceless set theory. As a specific class of such sentences, I consider the countable chromatic number of various (sigma-)algebraic hypergraphs on Euclidean spaces. A recent result deals with the graph G_n connecting points of rational distance in R^n: for every n>0, it is consistent with ZF+DC that the chromatic number of G_n is countable while that of G_{n+1} is not. TUESDAY, October 5, 2021 Set Theory Reading Group: 4:30 P.M., Online, Yuxin Zhou, University of Florida Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Distinguish coloring problems for isosceles triangle in R^2 and R^3 ABSTRACT: For n a positive natural number, let Γn be the hypergraph of isosceles triangles in R^n. Under the axiom of choice, the existence of a countable coloring for Γn is true for every n. Without the axiom of choice, the coloring problems will be hard to answer. With the existence of the inaccessible cardinal assumption, there is a model of ZF+DC in which Γ2 has countable chromatic number while Γ3 has uncountable chromatic number. This result is obtained by forcing over the symmetric Solovay model.

Wednesday seminar

Prague Set Theory Seminar
Dear all, The seminar meets on Wednesday October 6th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Noé de Rancourt -- A nonseparable version of Pełczyński's unconditional space Abstract: Pełczyński's unconditional space is a well-known example of a separable Banach space having a universal unconditional basis. It can be seen as a Fraïssé limit, and in particular, it has many nontrivial isometries. In a common work in progress with Ziemowit Kostana, we built a nonseparable version of this space in a forcing extension. Surprisingly, unlike its separable counterpart, our space is very rigid. In this talk, I will explain the construction of this space, show that it has few operators, and that all of its isometries are trivial. I will not assume any knowledge in Banach space theory, apart from a vague idea of what a Banach space is. The construction and the proofs I will present rely on almost no prerequisites in functional analysis, so I will be able to introduce everything during the talk. Best, David

Logic Seminar 6 Oct 2021 16:00 hrs at NUS by Chong Chitat

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 6 October 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Chong Chitat Title: First-order strength of tree colorings Abstract: In this talk we discuss the proof-theoretic strength, from the reverse mathematics perspective, of combinatorial principles concerning the coloring of binary trees and finite products of binary trees. Beginning with the principle TT^1, which states that every finite coloring of the full binary tree has an isomorphic monochromatic subtree, we will cover its strengthening to the existence of a strong monochromatic subtree, and to the full generalization of the latter known as the Halpern-Laeuchli Theorem. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

This Week in Logic at CUNY - UPDATE

This Week in Logic at CUNY
Hi everyone,

Please see the addition of tomorrow's (Tuesday 9/28) talk in the Computational Logic Seminar.

Best,
Jonas



This Week in Logic at CUNY:


- - - - Tuesday, Sep 28, 2021 - - - -

Computational Logic Seminar
Tuesday September 28, 2021, 2-4pm
For a zoom link, contact Sergei Artemov (sartemov@gc.cuny.edu)
Speaker: Melvin Fitting, CUNY Graduate Center
Title: Admitting the Empty Domain

Abstract.  Classical logic is almost always formulated with the empty domain not allowed.  Still, we do understand quantification over the empty domain.  So why the discrepancy?  Allowing the empty domain was investigated axiomatically by a couple of well-known people in the 1950’s and 1960’s, but this had no real effect.  It turns out there are two versions of what is called “Inclusive” logic, allowing the empty domain.  I looked at this using tableaus, 50 years ago, and found that the difference between the two versions was easy to understand with tableau machinery.  Recently I went back and looked at the work again, and found that the two versions actually differ on interpolation.  One version has interpolants, the other doesn’t.  A curious result, certainly..

This talk is about classical logic.  But the same issues come up for intuitionistic logic, modal logics, paraconsistent logics, and so on.  Nobody seems to have looked at what happens.  At the heart of it all, the original question that prompted the investigations of the 1960’s still remains: why should the existence of something be taken as a logical truth?



- - - - Wednesday, Sep 29, 2021 - - - -



- - - - Thursday, Sep 30, 2021 - - - -



- - - - Friday, Oct 01, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 1
The seminar will take place virtually at 11:30am US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Matteo Viale, University of Torino
Absolute model companionship, forcibility, and the continuum problem: Part II

Absolute model companionship (AMC) is a strengthening of model companionship defined as follows: For a theory  denotes the logical consequences of  which are boolean combinations of universal sentences.  is the AMC of  if it is model complete and . The -theory  of algebraically closed field is the model companion of the theory of  but not its AMC as . Any model complete theory  is the AMC of . We use AMC to study the continuum problem and to gauge the expressive power of forcing. We show that (a definable version of)  is the unique solution to the continuum problem which can be in the AMC of a partial Morleyization of the -theory there are class many supercompact cardinals. We also show that (assuming large cardinals) forcibility overlaps with the apparently weaker notion of consistency for any mathematical problem  expressible as a -sentence of a (very large fragment of) third order arithmetic (, the Suslin hypothesis, the Whitehead conjecture for free groups are a small sample of such problems ). Partial Morleyizations can be described as follows: let  be the set of first order -formulae; for  is the expansion of  adding atomic relation symbols  for all formulae  in  and  is the -theory asserting that each -formula  is logically equivalent to the corresponding atomic formula . For a -theory   is the partial Morleyization of  induced by .



Next Week in Logic at CUNY:

- - - - Monday, Oct 4, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 4, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Rushed Ahmad, UConn




- - - - Tuesday, Oct 5, 2021 - - - -



- - - - Wednesday, Oct 6, 2021 - - - -



- - - - Thursday, Oct 7, 2021 - - - -



- - - - Friday, Oct 8, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 8
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Brent Cody, Virginia Commonwealth University
Higher derived topologies





- - - - Other Logic News - - - -

ANNOUNCEMENT - Carl Posy - Working Group on Intuitionism

I am assembling a working group on intuitionism.  We aim eventually to explore the philosophical ground of intuitionistic mathematics.  We will ultimately look at issues in philosophy of mind (including phenomenology), epistemology, ontology and semantics. However, in order to do so, we will begin with in depth studies of intuitionistic mathematics and intuitionistic logic.

Participation in the group will provide the needed background for someone who would like to develop large or small projects related to some aspect of intuitionism (mathematics, logic or philosophy).  The group will also serve those who are interested simply in acquiring a working knowledge of intuitionism per se.

Our initial studies of intuitionistic mathematics and logic will roughly follow the organization of the first chapters of my recent book Mathematical Intuitionism.  However, we will refine, correct and expand the material in the book.  There’ll be references and material for those who would like to pursue some topic or other even further.

The group invites both participants with some limited or even extensive background in intuitionism and those without any background in intuitionism but with an interest in learning about intuitionism and/or working on related research aims.  Some knowledge of mathematics (in particular of elementary real analysis) and/or logic (in particular through basic philosophical logic) is desirable.  

The group will have regularly scheduled meetings no more frequently than twice a month, during the academic year.  We will set a schedule at the start of each year.  

The current plan is to function for at least two or three academic years.  Sometime in the second or third year we will have a conference including members and outside researchers. We will begin in late 2021 or early 2022.  

From time to time will also have guest lectures from prominent researchers.

From time to time active members will  prepare and present material  -- appropriate to their background and interests.  

Anyone interested should contact me at:  carl.posy@mail.huji.ac.il    We will then arrange a time to speak.


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Apologies for the late start this semester.  Regular weekly mailings of "This Week in Logic" will continue going forward - please send me your announcements for upcoming New York logic events.  Welcome back!

Best,
Jonas


This Week in Logic at CUNY:

- - - - Monday, Sep 27, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, September 27, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Speaker: Rashed Ahmad (University of Connecticut)
Title: A Recipe for Paradox: A Better Schema than the Inclosure Schema

Abstract: In this talk, we provide a recipe that not only captures the common structure between semantic paradoxes but it also captures our intuitions regarding the relations between these paradoxes. Before we unveil our recipe, we first talk about a popular schema introduced by Graham Priest, namely, the inclosure schema. Without rehashing previous arguments against the inclosure schema, we contribute different arguments for the same concern that the inclosure schema bundles the wrong paradoxes together. That is, we will provide alternative arguments on why the inclosure schema is both too broad for including the Sorites paradox, and too narrow for excluding Curry’s paradox. We then spell out our recipe. Our recipe consists of three ingredients: (1) a predicate that has two specific rules, (2) a simple method to find a partial negative modality, and (3) a diagonal lemma that would allow us to let sentences be their partial negative modalities. The recipe shows that all of the following paradoxes share the same structure: The liar, Curry’s paradox, Validity Curry, Provability Liar, a paradox leading to Löb’s theorem, Knower’s paradox, Knower’s Curry, Grelling-Nelson’s paradox, Russell’s paradox in terms of extensions, alternative liar and alternative Curry, and other unexplored paradoxes. We conclude the talk by stating the lessons that we can learn from the recipe, and what kind of solutions does the recipe suggest if we want to adhere to the Principle of Uniform Solution.



- - - - Tuesday, Sep 28, 2021 - - - -



- - - - Wednesday, Sep 29, 2021 - - - -



- - - - Thursday, Sep 30, 2021 - - - -



- - - - Friday, Oct 01, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 1
The seminar will take place virtually at 11:30am US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Matteo Viale, University of Torino
Absolute model companionship, forcibility, and the continuum problem: Part II

Absolute model companionship (AMC) is a strengthening of model companionship defined as follows: For a theory  denotes the logical consequences of  which are boolean combinations of universal sentences.  is the AMC of  if it is model complete and . The -theory  of algebraically closed field is the model companion of the theory of  but not its AMC as . Any model complete theory  is the AMC of . We use AMC to study the continuum problem and to gauge the expressive power of forcing. We show that (a definable version of)  is the unique solution to the continuum problem which can be in the AMC of a partial Morleyization of the -theory there are class many supercompact cardinals. We also show that (assuming large cardinals) forcibility overlaps with the apparently weaker notion of consistency for any mathematical problem  expressible as a -sentence of a (very large fragment of) third order arithmetic (, the Suslin hypothesis, the Whitehead conjecture for free groups are a small sample of such problems ). Partial Morleyizations can be described as follows: let  be the set of first order -formulae; for  is the expansion of  adding atomic relation symbols  for all formulae  in  and  is the -theory asserting that each -formula  is logically equivalent to the corresponding atomic formula . For a -theory   is the partial Morleyization of  induced by .



Next Week in Logic at CUNY:

- - - - Monday, Oct 4, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, October 4, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Rushed Ahmad, UConn




- - - - Tuesday, Oct 5, 2021 - - - -



- - - - Wednesday, Oct 6, 2021 - - - -



- - - - Thursday, Oct 7, 2021 - - - -



- - - - Friday, Oct 8, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center, Room 6417
Friday, October 8
The seminar will take place virtually at 2:00pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Brent Cody, Virginia Commonwealth University
Higher derived topologies





- - - - Other Logic News - - - -

ANNOUNCEMENT - Carl Posy - Working Group on Intuitionism

I am assembling a working group on intuitionism.  We aim eventually to explore the philosophical ground of intuitionistic mathematics.  We will ultimately look at issues in philosophy of mind (including phenomenology), epistemology, ontology and semantics. However, in order to do so, we will begin with in depth studies of intuitionistic mathematics and intuitionistic logic.

Participation in the group will provide the needed background for someone who would like to develop large or small projects related to some aspect of intuitionism (mathematics, logic or philosophy).  The group will also serve those who are interested simply in acquiring a working knowledge of intuitionism per se.

Our initial studies of intuitionistic mathematics and logic will roughly follow the organization of the first chapters of my recent book Mathematical Intuitionism.  However, we will refine, correct and expand the material in the book.  There’ll be references and material for those who would like to pursue some topic or other even further.

The group invites both participants with some limited or even extensive background in intuitionism and those without any background in intuitionism but with an interest in learning about intuitionism and/or working on related research aims.  Some knowledge of mathematics (in particular of elementary real analysis) and/or logic (in particular through basic philosophical logic) is desirable.  

The group will have regularly scheduled meetings no more frequently than twice a month, during the academic year.  We will set a schedule at the start of each year.  

The current plan is to function for at least two or three academic years.  Sometime in the second or third year we will have a conference including members and outside researchers. We will begin in late 2021 or early 2022.  

From time to time will also have guest lectures from prominent researchers.

From time to time active members will  prepare and present material  -- appropriate to their background and interests.  

Anyone interested should contact me at:  carl.posy@mail.huji.ac.il    We will then arrange a time to speak.


- - - - Web Site - - - -

Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)

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Two events on Tuesday 9/28/21

Carnegie Mellon Logic Seminar
TUESDAY, September 28, 2021 Mathematical logic seminar: 3:30 P.M., Online, Thomas Gilton, University of Pittsburgh Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: The tension between reflection/compactness and rigidity in combinatorial set theory ABSTRACT: The aim of this talk is to provide background with which to motivate a recent joint result of the speaker with Omer Ben-Neria. This result concerns the tension between two classes of combinatorial principles in set theory, namely reflection/compactness principles on the one hand and incompactness/anti-reflection properties on the other. The rigidity implied by the latter class often suffices to prove the negation of principles in the former class, and as a result, a large research program in set theory is dedicated to investigating when principles from these two classes are jointly consistent. Our theorem - that the Special Aronszajn Tree Property is consistent with Club Stationary Reflection on $\omega_2$ - is such a result. We will discuss this tension historically before showing how, in our result, the tension shows up in our proof, especially in the radically different properties of our posets which we have to maintain throughout the course of our construction. TUESDAY, September 28, 2021 Set Theory Reading Group: 4:30 P.M., Online, Thomas Gilton, University of Pittsburgh Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Club stationary reflection and the special Aronszajn tree property ABSTRACT: In this talk, we will dive into the technical details of our result with Omer Ben-Neria. We will first show how to specialize trees on $\omega_2$ with a preparatory forcing which is no longer $\kappa$-c.c., as in the classic setting of Laver and Shelah. Rather, this preparatory forcing will satisfy a kind of $\kappa$-strong properness which is witnessed by continuous residue functions like those used in various side conditions iteration theorems of Itay Neeman. We then show how to build posets satisfying this kind of $\kappa$-strong properness by following a Levy collapse of a weakly compact with a class of posets we call $\mathcal{F}_{WC}$-completely proper, where $\mathcal{F}_{WC}$ is the weakly compact filter. This is similar to Abraham's use of guiding reals to obtain strong properness for countable models. We then close by gesturing to solutions of the technical problems which remain, particularly ones involving new preservation theorems for Aronszajn trees and stationary sets.

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Zhixing You (Universitat de Barcelona)
TITLE: 
DATE: 29 September 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online via Zoom:



Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.












Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609















Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
joan.bagaria@icrea.cat
bagaria@ub.edu


Event Tuesday, September 21

Carnegie Mellon Logic Seminar
TUESDAY, September 21, 2021 Set Theory Reading Group: 4:30 P.M., Online, Allison Wang, Carnegie Mellon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Hyperfiniteness and Ramsey notions of largeness ABSTRACT: The lowest non-trivial complexity class in the theory of Countable Borel Equivalence Relations (CBERs) is the class of hyperfinite CBERs. One difficulty that arises in studying this class is determining which CBERs are hyperfinite. Measure theory can be used to answer this question, but not many techniques can. For instance, a Baire category approach cannot distinguish hyperfinite CBERS: a result of Hjorth and Kechris states that every CBER on a Polish space is hyperfinite when restricted to some comeager set. We will discuss a classical proof of Mathias's theorem that every CBER on the Ellentuck Ramsey space is hyperfinite when restricted to some pure Ellentuck cube. Mathias's theorem implies that a Ramsey-theoretic approach also cannot distinguish hyperfinite CBERs. This is joint work with Aristotelis Panagiotopoulos. ORGANIZER'S NOTE: The talk will start after some socializing, at around 4:40 or 4:45.

Wednesday seminar

Prague Set Theory Seminar
Dear all, We will restart the Wednesday seminar again this autumn. Hopefully we will not need pause it because of the pandemic again. The seminar should meet at the usual time and place, starting on Wednesday September 29. Please let me know in case you would know any email addresses I should add to the mailing list, or in case you would like to be removed from the list. The seminar meets on Wednesday September 29th at 11:00 in the Institute of Mathematics CAS, Zitna 25, seminar room, 3rd floor, front building. Program: Chris Lambie Hanson -- Strongly unbounded functions and productivity of chain conditions We discuss the existence of strongly unbounded functions on pairs of ordinals, which provide strong counterexamples to generalizations of Ramsey's theorem to uncountable cardinals. The talk will include a brief, gentle introduction to Todorcevic's powerful technique of walks on ordinals and an application to the infinite productivity of the $\kappa$-Knaster property. Some of the results are joint work with Assaf Rinot. Best, David

Logic Seminar Wed 15 Sept 2021 16:00 hrs at NUS by Bakhadyr Khoussainov

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 15 September 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Bakhadyr Khoussainov, UESTC, Chengdu and The University of Auckland Title: Probability Structures URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: This talk belongs to the area of probabilistic logic semantics. The first contribution of this work is the introduction of probability structures. Probability structures are the algebraic structures equipped with probability functions on the domains and the atomic predicates. These structures extend type 1 probability structures introduced by Halpern and Bacchus. Type 1 probability structures contain probability functions on domains only. Our probability structures possess an additional statistical knowledge, - probability functions on atomic predicates. We present a method that builds probability spaces for the first order logic formulas and prove that our semantics is sound. The second contribution of this work is the introduction of smooth probability structures. The smooth probability structures carefully refine probability structures so that we have a better control of the probability spaces defined by first order logic formulas. For these structures we initiate the study of first order probability logic (FOPLS), investigate axiomatizability of FOPLS, and address decidability and undecidability questions of the sets of valid formulas. We also study a few algorithmic questions on probability structures.

Logic Seminar Today 16:00 hrs SGT at NUS by Khoussainov and Stephan

NUS Logic Seminar
Hello, the password of this reminder was wrong, here the amended version. Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 8 September 2021, 16:00 hrs, Singapore Time Zone (GMT+8 hrs) Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Bakhadyr Khoussainov and Frank Stephan Title: Parity Games - Background and Algorithms. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Parity games are games where a marker is moved on a finite graph and each node is annotated with a natural number; the game runs forever and the largest number in an infinitely often visited node decides the winner, if it is even then player Anke wins else player Boris wins. Marcin Jurdzinski showed that this game is in UP intersected coUP and also provided the first not fully exponential algorithm for it; however, the exact time complexity remained unresolved. In 2017, Calude, Jain, Khoussainov, Li and Stephan found a quasipolynomial time algorithm which Jurdzinski and Lazic as well as Fearnley, Jain, Schewe, Stephan and Wojtczak improved the algorithm to be in polynomial space as well as quasipolynomial time. The talk provides the way this algorithm was found and the implications it has for the fixed-parameter-tracktability of parity games and related problems like coloured Muller games. Though now quite a number of quasipolynomial time algorithms are known and there is quite extensive research in this topic, the question on whether parity games can even be solved in polynomial time is still unresolved. This talk is given by Bakhadyr Khoussainov and Frank Stephan jointly also on behalf of their coauthors Cristian Calude, Sanjay Jain and Wei Li.

Logic Seminar Today 16:00 hrs SGT at NUS by Khoussainov and Stephan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 8 September 2021, 16:00 hrs, Singapore Time Zone (GMT+8 hrs) Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=3DUWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=3Dx3+y3 Speaker: Bakhadyr Khoussainov and Frank Stephan Title: Parity Games - Background and Algorithms. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Parity games are games where a marker is moved on a finite graph and each node is annotated with a natural number; the game runs forever and the largest number in an infinitely often visited node decides the winner, if it is even then player Anke wins else player Boris wins. Marcin Jurdzinski showed that this game is in UP intersected coUP and also provided the first not fully exponential algorithm for it; however, the exact time complexity remained unresolved. In 2017, Calude, Jain, Khoussainov, Li and Stephan found a quasipolynomial time algorithm which Jurdzinski and Lazic as well as Fearnley, Jain, Schewe, Stephan and Wojtczak improved the algorithm to be in polynomial space as well as quasipolynomial time. The talk provides the way this algorithm was found and the implications it has for the fixed-parameter-tracktability of parity games and related problems like coloured Muller games. Though now quite a number of quasipolynomial time algorithms are known and there is quite extensive research in this topic, the question on whether parity games can even be solved in polynomial time is still unresolved. This talk is given by Bakhadyr Khoussainov and Frank Stephan jointly also on behalf of their coauthors Cristian Calude, Sanjay Jain and Wei Li.

Logic Seminar 8 September 2021 16:00 hrs at NUS by Bakhadyr Khoussainov and Frank Stephan

NUS Logic Seminar
Hello, there is a typing error in the below email. It should be "8 September 2021", so Wednesday next week. Frank Stephan On Thu, Sep 02, 2021 at 11:18:49PM +0800, Frank STEPHAN wrote: > Invitation to the Logic Seminar at the National University of Singapore > > Date: Wednesday, CORRECTED TO 08 Sep 2021, 16:00 hrs > > Talk via Zoom: > https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 > Meeting ID: 830 4925 8042 > Passcode: 1729=x3+y3 > > Speaker: Bakhadyr Khoussainov and Frank Stephan > > Title: Parity Games - Background and Algorithms. > > URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html > > Abstract: > Parity games are games where a marker is moved on > a finite graph and each node is annotated with a > natural number; the game runs forever and the largest > number in an infinitely often visited node decides > the winner, if it is even then player Anke wins > else player Boris wins. Marcin Jurdzinski showed > that this game is in UP intersected coUP and also > provided the first not fully exponential algorithm > for it; however, the exact time complexity remained > unresolved. In 2017, Calude, Jain, Khoussainov, Li > and Stephan found a quasipolynomial time algorithm > which Jurdzinski and Lazic as well as Schewe and his > collaborators improved to be in polynomial space > as well. The talk provides the way this algorithm > was found and the implications it has for the > fixed-parameter-tracktability of parity games and > related problems like coloured Muller games. Though > now quite a number of quasipolynomial time algorithms > are known and there is quite extensive research in this > topic, the question on whether parity games can even > be solved in polynomial time is still unresolved. > > This talk is given by Bakhadyr Khoussainov and > Frank Stephan jointly also on behalf of their coauthors > Cristian Calude, Sanjay Jain and Wei Li. >

Logic Seminar 8 September 2021 16:00 hrs at NUS by Bakhadyr Khoussainov and Frank Stephan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 11 August 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Bakhadyr Khoussainov and Frank Stephan Title: Parity Games - Background and Algorithms. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Parity games are games where a marker is moved on a finite graph and each node is annotated with a natural number; the game runs forever and the largest number in an infinitely often visited node decides the winner, if it is even then player Anke wins else player Boris wins. Marcin Jurdzinski showed that this game is in UP intersected coUP and also provided the first not fully exponential algorithm for it; however, the exact time complexity remained unresolved. In 2017, Calude, Jain, Khoussainov, Li and Stephan found a quasipolynomial time algorithm which Jurdzinski and Lazic as well as Schewe and his collaborators improved to be in polynomial space as well. The talk provides the way this algorithm was found and the implications it has for the fixed-parameter-tracktability of parity games and related problems like coloured Muller games. Though now quite a number of quasipolynomial time algorithms are known and there is quite extensive research in this topic, the question on whether parity games can even be solved in polynomial time is still unresolved. This talk is given by Bakhadyr Khoussainov and Frank Stephan jointly also on behalf of their coauthors Cristian Calude, Sanjay Jain and Wei Li.

Logic Seminar today 16:00 hrs at NUS by Rupert Hoelzl, University of the Bundeswehr in Munich

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 1 September 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl Title: The reverse mathematics of inductive inference URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: We investigates inductive inference from the perspective of reverse mathematics. Reverse mathematics is a framework that allows gauging the proof strength of theorems and axioms in many areas of mathematics. We apply its methods to basic notions of algorithmic learning theory such as Angluin's tell-tale criterion and its variants for learning in the limit and for conservative learning, as well as to the more general scenario of partial learning. These notions are studied in the reverse mathematics context for uniformly and weakly represented families of languages. The results are stated in terms of axioms referring to induction strength and to domination of weakly represented families of functions.

Free Registration for IPEC 2021 until 29 August 2021 (Online Conference)

NUS Logic Seminar
Hello, Most likely on 8 September 2021, Bakhadyr Khoussainov and Frank Stephan will give an invited talk about the paper Deciding parity games in quasipolynomial time by Cristian Calude, Sanjay Jain, Bakhadyr Khoussainov, Wei Li and Frank Stephan from STOC 2017 and SIAM Journal on Computing at IPEC 2021. You can up to tomorrow (29 August 2021) register for free at this online occurring conference through the webpage http://algo2021.tecnico.ulisboa.pt/index.html#registration and information on the conference IPEC is on http://algo2021.tecnico.ulisboa.pt/IPEC2021/index.html The exact programme is not yet there, but will most likely be made available after tomorrow's free registration deadline for nonpresenting participants. IPEC is an International Symposium on Parameterised and Exact Computation. Sorry for the short notice, I was waiting for info about the conference going onto the webpage before sending this. Best regards, Frank

Felix Weilacher on Tuesday (8/31) 3:30 PM Eastern

Carnegie Mellon Logic Seminar
TUESDAY, August 31 2021 Mathematical logic seminar: 3:30 P.M., Online, Felix Weilacher, Carnegie Mellon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Borel Edge Colorings for Finite Dimensional Groups ABSTRACT: In Borel graph combinatorics, one often produces a structure (e.g. a coloring) by dividing a graph into subgraphs with finite connected components, then defining the structure on those components via some straightforward uniformization result. We first give an overview of some recent work formalizing these notions and applying them to various problems. We then present our own application to the problem of edge coloring. For Borel actions of certain groups, we find "degree plus one" Borel edge colorings, matching the classical bound of Vizing. Furthermore, for finitely generated abelian groups, we are able to exactly determine Borel edge chromatic numbers.

Logic Seminar 1 Sept 2021 16:00 hrs at NUS by Rupert Hoelzl, Univ. of the Bundeswehr, Munich

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 1 September 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Rupert Hoelzl Title: The reverse mathematics of inductive inference URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html We investigates inductive inference from the perspective of reverse mathematics. Reverse mathematics is a framework that allows gauging the proof strength of theorems and axioms in many areas of mathematics. We apply its methods to basic notions of algorithmic learning theory such as Angluin's tell-tale criterion and its variants for learning in the limit and for conservative learning, as well as to the more general scenario of partial learning. These notions are studied in the reverse mathematics context for uniformly and weakly represented families of languages. The results are stated in terms of axioms referring to induction strength and to domination of weakly represented families of functions.

Logic Seminar 25 April 2021 16:00 hrs by Ng Keng Meng (NTU) at NUS (today)

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 25 August 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Ng Keng Meng Title: Are the rationals dense Abstract: There has been a recent revival in the interest in sub-computable mathematics. One of these approaches is to consider ``primitive recursive'' or punctual structures. This has led to a greater understanding in the effective content of well-known objects and proofs in classical computability theory. When considering the punctual anaologies of classical computabilitiy we often obtain strange and surprising results. I will discuss some recent work in progress in this area, focussing particularly on structural results. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

RIMS Set Theory Workshop: October 12-15, 2021

Conference
RIMS SET THEORY WORKSHOP 2021 Announcement / Call for Contributions RIMS workshop "Recent Developments in Set Theory of the Reals" Date: Tuesday, October 12, 2021 to Friday, October 15, 2021 Venue: ONLINE (via ZOOM meeting), based on Japan Standard Time 9am--5pm Contact: Masaru Kada (Osaka Prefecture University) / kada@mi.s.osakafu-u.ac.jp Workshop Overview: This online workshop, hosted by RIMS (Research Institute for Mathematical Sciences, Kyoto University), is mainly (but not only) focused on recent developments in set theory of the reals. The program will contain a minicourse (a series of lectures) as well as contributed talks. In the minicourse, we invite Joerg Brendle (Kobe University) and Diego Mejia (Shizuoka University), who will give us lectures on some forcing techniques (e.g., Boolean ultrapowers, submodel methods, etc.) and related results in set theory of the reals. We welcome every researcher in set theory or related research fields. Please join us! Registration: Please submit a registration form to register your participation / contributed talk, from the following URL: https://forms.gle/1156YFMp1bN9GEDJ9 Deadline for contributed talks: September 9, 2021 Deadline for participation: October 10, 2021

First math logic seminar of the new semester

Carnegie Mellon Logic Seminar
TUESDAY, August 31 2021 Mathematical logic seminar: 3:30 P.M., Online, Felix Weilacher, Carnegie Mellon University Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Borel Edge Colorings for Finite Dimensional Groups ABSTRACT: In Borel graph combinatorics, one often produces a structure (e.g. a coloring) by dividing a graph into subgraphs with finite connected components, then defining the structure on those components via some straightforward uniformization result. We first give an overview of some recent work formalizing these notions and applying them to various problems. We then present our own application to the problem of edge coloring. For Borel actions of certain groups, we find "degree plus one" Borel edge colorings, matching the classical bound of Vizing. Furthermore, for finitely generated abelian groups, we are able to exactly determine Borel edge chromatic numbers.

Logic Seminar at NUS on Wed 18 Aug 2021 at 16:00 hrs

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 18 August 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Yu Liang, Nanjing University Title: Generalizing Besicovitch-Davis theorem URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Besicovitch-Davis theorem says that the Hausdorff dimension of every analytic set can be approximated by its closed subset. But the Besicovitch-Davis theorem fails for co-analytic sets under the assumption V=L as observed by Slaman. We prove that the theorem holds for arbitrary sets under ZF+sTD. We also prove that the theorem holds for Sigma-1-2-sets under Martin's axiom. This is joint work with Peng Yinhe and Wu Liuzhen.

Logic Seminar 11 Aug 2021 16:00 hrs at NUS by Frank Stephan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 11 August 2021, 16:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/83049258042?pwd=UWViaWNvTFUrdFdhOHJCdEVydnVkdz09 Meeting ID: 830 4925 8042 Passcode: 1729=x3+y3 Speaker: Frank Stephan Title: A survey on the structures realised by positive equivalence relations URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Let a positive equivalence relation to be an r.e. equivalence relation on the set of natural numbers with infinitely many equivalence relations. Khoussainov initiated with coauthors a deep study of the following question: Given a positive equivalence relation eta, which structures from a given set of structures does this equivalence relation realise? Here realisation means that functions in the structure are recursive and relations are r.e. with the equality itself given by the equivalence relation eta. In other words, the given r.e. structure divided by eta is the structure realised by eta. Now questions studied by Khoussainov and his coworkers included questions like "What is the partial ordering on positive equivalence relations eta,rho where eta is below rho iff every structure of the given type realised by eta is also realised by rho? Besides algebraic structures and orders, it has also been studied how the learnability notions behave with respect to uniformly r.e. one-one families realised by positive equivalence relations.

Events next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, August 10 2021 Mathematical logic seminar: 3:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 6) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic. TUESDAY, August 10, 2021 Set Theory Reading Group: 4:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 7) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic.

Events next Tuesday

Carnegie Mellon Logic Seminar
ORGANIZER'S NOTE: Video recordings of Nathaniel Bannister's seminar series are being made available online. Please email me for details if you would like access. TUESDAY, August 3, 2021 Mathematical logic seminar: 3:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 4) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic. TUESDAY, August 3, 2021 Set Theory Reading Group: 4:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 5) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic.

Logic seminar and set theory reading group for next week

Carnegie Mellon Logic Seminar
ORGANIZERS' NOTE: Last week, these seminars were postponed until next week due to last minute technical issues. -------------------------------------------------------------------------- TUESDAY, July 27, 2021 Mathematical logic seminar: 3:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 2) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic. TUESDAY, July 27, 2021 Set Theory Reading Group: 4:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Zoom link: https://cmu.zoom.us/j/621951121?pwd=eWEwVit5WUxlUExOWE51ajdFZnJ2Zz09 Meeting ID: 621 951 121 Passcode: 617076 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 3) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic.

An apology to all about today's seminar

Toronto Set Theory Seminar
Hello everyone,

As some of you noticed, today there was no seminar although it was announced and not cancelled. We are very sorry about this miscommunication on our end.

Also, I offer an apology to everyone for not being in the meeting to explain the situation.

Last minute yesterday, we found out that the speaker was not going to be able to assist. I was supposed to send an email cancelling the seminar today, but I didn't.

Today I got my first vaccine shot so my mind was elsewhere (along with my internet and my computer), so I was not able to warn everyone about the cancellation.

Again, we offer an apology. This speaker will be able to participate in the seminar in september. In the meanwhile, we do not have seminar next week.

I thank everyone for your comprehension.

Best regards

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk tomorrow by Gianluca Paolini at 1 30 pm (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:Gianluca Paolini
Date and Time: Friday, July 23rd, 2021 - 1:30pm to 3:00pm
Title: Torsion-Free Abelian Groups are Borel Complete
Abstract:
We prove that the Borel space of torsion-free Abelian groups with domain is Borel complete, i.e., the isomorphism relation on this Borel space is as complicated as possible, as an isomorphism relation. This solves a long-standing open problem in descriptive set theory, which dates back to the seminal paper on Borel reducibility of Friedman and Stanley from 1989.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk Friday 23rd June by Gianluca Paolini at 1 30 pm (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:Gianluca Paolini
Date and Time: Friday, July 23rd, 2021 - 1:30pm to 3:00pm
Title: Torsion-Free Abelian Groups are Borel Complete
Abstract:
We prove that the Borel space of torsion-free Abelian groups with domain is Borel complete, i.e., the isomorphism relation on this Borel space is as complicated as possible, as an isomorphism relation. This solves a long-standing open problem in descriptive set theory, which dates back to the seminal paper on Borel reducibility of Friedman and Stanley from 1989.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk in ONE hour by Richard Matthews

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Richard Matthews
Date and Time: Friday, July 16th, 2021 - 1:30pm to 3:00pm
Title: Large Cardinals in Weakened Axiomatic Theories
Abstract:
The Kunen Inconsistency is an important milestone in the study of axiomatic set theory, placing a hard limit on how close the target model of a non-trivial elementary embedding can be to the full universe. In particular, it shows that the existence of a Reinhardt embedding, that is a non-trivial embedding of the full universe into itself, is inconsistent. It is well-known that all proofs we currently have rely extensively on the fact that we are working with the full power of ZFC, most notably the essential use of choice.

In this talk we shall discuss the notion of a Reinhardt embedding over several weakened base theories, primarily ZFC without Power Set, Zermelo and Power Kripke Platek. We shall see how to obtain some upper bounds, lower bounds and equiconsistency results in terms of the usual ZFC large cardinal hierarchy as well as many unexpected characteristics such embeddings can have. Moreover, we shall see that, under reasonable additional assumptions, it is possible to reobtain Kunen-type inconsistency results in both ZFC without Power Set and Power Kripke Platek plus Well-Ordering.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Events next Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, July 20, 2021 Mathematical logic seminar: 3:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 2) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic. TUESDAY, July 20, 2021 Set Theory Reading Group: 4:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 3) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic.

Today at 1 30 pm talk by Richard Matthews (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Richard Matthews
Date and Time: Friday, July 16th, 2021 - 1:30pm to 3:00pm
Title: Large Cardinals in Weakened Axiomatic Theories
Abstract:
The Kunen Inconsistency is an important milestone in the study of axiomatic set theory, placing a hard limit on how close the target model of a non-trivial elementary embedding can be to the full universe. In particular, it shows that the existence of a Reinhardt embedding, that is a non-trivial embedding of the full universe into itself, is inconsistent. It is well-known that all proofs we currently have rely extensively on the fact that we are working with the full power of ZFC, most notably the essential use of choice.

In this talk we shall discuss the notion of a Reinhardt embedding over several weakened base theories, primarily ZFC without Power Set, Zermelo and Power Kripke Platek. We shall see how to obtain some upper bounds, lower bounds and equiconsistency results in terms of the usual ZFC large cardinal hierarchy as well as many unexpected characteristics such embeddings can have. Moreover, we shall see that, under reasonable additional assumptions, it is possible to reobtain Kunen-type inconsistency results in both ZFC without Power Set and Power Kripke Platek plus Well-Ordering.



Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Two events on Tuesday

Carnegie Mellon Logic Seminar
TUESDAY, July 13, 2021 Mathematical logic seminar: 3:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: An introduction to strong homology ABSTRACT: We will introduce strong homology, which aims to correct the failures of Čech homology, particularly the failure of exactness. TUESDAY, July 13, 2021 Set Theory Reading Group: 4:30 P.M., Online, Nathaniel Bannister, Carnegie Mellon University (beginning Fall, 2021) Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Additivity of strong homology for locally compact separable metric spaces (part 1) ABSTRACT: This series of talks will cover the 2019 paper "On the additivity of strong homology for locally compact separable metric spaces" as well as recent work establishing a conceptual basis for the results therein. We will show that (relative to a weakly compact cardinal) it is consistent for strong homology to be additive and compactly supported on the class of locally compact separable metric spaces. In the process, we develop an equivalent algebraic statement and a sufficient cardinal-theoretic condition. This is joint work with Justin Moore, Jeffrey Bergfalk, and Stevo Todorcevic.

Talk Tomorrow by Osvaldo Guzmán 1 30 pm (Totonto time)

Toronto Set Theory Seminar
  Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance. See attached image or follow the link below.


Here the speaker information:

Speaker:  Osvaldo Guzmán González
Date and Time: Friday, July 9th, 2021 - 1:30pm to 3:00pm
Title: MAD families and strategically bounding forcings
Abstract:
The notion of strategically bounding forcings is a natural game-theoretic
strengthening of the bounding property for partial orders.  In this talk, we
will study the basic properties of strategically bounding forcings and talk
about indestructibility of MAD families. The motivation for this work is the
problem of Roitman. I will talk about results that were obtained with
Michael Hrusak, Joerg Brendle and Dilip Raghavan.
Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Series finale

Carnegie Mellon Logic Seminar
TUESDAY, July 6, 2021 Mathematical logic seminar: 3:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Homological algebra for logicians ABSTRACT: This is part 7 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module). TUESDAY, July 6, 2021 Set Theory Reading Group: 4:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Homological algebra for logicians ABSTRACT: This is part 8 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module).

Talk this Friday (July 9th) by Osvaldo Guzmán 1 30 pm (Totonto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.

TBD

Here the speaker information:

Speaker:  Osvaldo Guzmán González
Date and Time: Friday, July 9th, 2021 - 1:30pm to 3:00pm
Title: MAD families and strategically bounding forcings
Abstract:
The notion of strategically bounding forcings is a natural game-theoretic
strengthening of the bounding property for partial orders.  In this talk, we
will study the basic properties of strategically bounding forcings and talk
about indestructibility of MAD families. The motivation for this work is the
problem of Roitman. I will talk about results that were obtained with
Michael Hrusak, Joerg Brendle and Dilip Raghavan.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

James Cummings series continues

Carnegie Mellon Logic Seminar
TUESDAY, June 29, 2021 Mathematical logic seminar:  3:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Homological algebra for logicians ABSTRACT: This is part 5 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module). TUESDAY, June 29, 2021 Set Theory Reading Group:  4:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Homological algebra for logicians ABSTRACT: This is part 6 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module).

Talk TODAY by Riley Thornton 1 30 pm (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:   Riley Thornton
Date and Time: Friday, June 25th, 2021 - 1:30pm to 3:00pm
Title: Effectivization in Borel Combinatorics
Abstract:
In Borel combinatorics, we often want to know when a Borel graph (or equivalence relation, quasi-order, etc) admits a Borel witness to some combinatorial property, . An effectivization theorem for says that any (lightface) graph with a Borel witness to in fact has a witness. This kind of effectivization gives a strong upper bound on the projective complexity of the set of graphs where a definable witness exists and suggests that such graphs might admit a nice structural characterization. This talk will present a streamlined method for proving effectivization theorems, give a number of applications, and discuss some related dichotomy theorems.

Please visit http://www.fields.utoronto.ca/talks/Effectivization-Borel-Combinatorics for a cleaner version of the abstract.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk this Friday 25th (in less than two days) by Riley Thornton 1 30 pm (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:   Riley Thornton
Date and Time: Friday, June 25th, 2021 - 1:30pm to 3:00pm
Title: Effectivization in Borel Combinatorics
Abstract:
In Borel combinatorics, we often want to know when a Borel graph (or equivalence relation, quasi-order, etc) admits a Borel witness to some combinatorial property, . An effectivization theorem for says that any (lightface) graph with a Borel witness to in fact has a witness. This kind of effectivization gives a strong upper bound on the projective complexity of the set of graphs where a definable witness exists and suggests that such graphs might admit a nice structural characterization. This talk will present a streamlined method for proving effectivization theorems, give a number of applications, and discuss some related dichotomy theorems.

Please visit http://www.fields.utoronto.ca/talks/Effectivization-Borel-Combinatorics for a cleaner version of the abstract.

I'll send the next reminder in the morning of the day of the talk


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk on Thursday, June 24

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, June 24 "Preserving levels of projective determinacy and regularity properties" Johannes Schürz (TU Wien) Since \mathbf{\Pi}^1_1-determinacy is a desirable property on the reals, the natural question arises as to how one can preserve it under forcing. We will show using the technique of capturing that the statement 'Every real has a sharp' is preserved under any countable support iteration of 'simply' definable forcing notions. By the famous results of L. Harrington and D. Martin this shows that \mathbf{\Pi}^1_1-determinacy is preserved under such iterations. More generally, our theorem also shows that the statement 'M_n^\sharp(x) exists for every real x \in \omega^\omega' is preserved. By the results of I. Neeman and H. Woodin this generalizes our result to higher levels of projective determinacy. Without the existence of large cardinals the technique of capturing can still be used to show preservation results for regularity properties such as the \mathbf{\Delta}^1_2- or \mathbf{\Sigma}^1_2-Baire property. This is a joint project with J. Schilhan and P. Schlicht. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Talk tomorrow 18th by David Schrittesser (1:30 pm to 3pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:  David Schrittesser
Date and Time: Friday, June 18th, 2021 - 1:30pm to 3:00pm
Title:  A taste of nonstandard analysis and statistical decision theory
Abstract:
Statistical decision theory takes inspiration from game theory to
provide a basic framework in which one can reason about optimality (or
lack thereof) of statistical methods, such as estimators and tests.
One (very weak) property of such methods is admissibility - roughly, a
method of estimation is admissible if there is no other which does
better under all circumstances (in a sense specified by the decision
theoretical framework).

Although a weak property, admissibility is notoriously hard to
characterize. Recently we have found a characterization of admissibility
(in a large class of statistical problems) in Bayesian terms, by using
prior probability distributions which can take on infinitesimal values.

(The talk will not presuppose any knowledge on statistics or nonstandard
analysis. Joint work with D. Roy and H. Duanmu.)
Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk this Friday 18th by David Schrittesser (1:30 pm to 3pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker:  David Schrittesser
Date and Time: Friday, June 18th, 2021 - 1:30pm to 3:00pm
Title:  A taste of nonstandard analysis and statistical decision theory
Abstract:
Statistical decision theory takes inspiration from game theory to
provide a basic framework in which one can reason about optimality (or
lack thereof) of statistical methods, such as estimators and tests.
One (very weak) property of such methods is admissibility - roughly, a
method of estimation is admissible if there is no other which does
better under all circumstances (in a sense specified by the decision
theoretical framework).

Although a weak property, admissibility is notoriously hard to
characterize. Recently we have found a characterization of admissibility
(in a large class of statistical problems) in Bayesian terms, by using
prior probability distributions which can take on infinitesimal values.

(The talk will not presuppose any knowledge on statistics or nonstandard
analysis. Joint work with D. Roy and H. Duanmu.)


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk and master defense Michael Zechner

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, June 17 "Big Ramsey degrees of 3-uniform hypergraphs are finite" David Chodounský (Czech Academy of Sciences) It is well known that the (universal countable) Rado graph has finite big Ramsey degrees. I.e., given a finite colouring of n-tuples of its vertices there is a copy of the Rado graph such that its n-tuples have at most D(n)-many colours. The proof of this fact uses a theorem of Milliken for trees, I will give sketch of the argument. I will moreover sketch an extension of the proof which works also for universal structures with higher arities, in particular 3-uniform hypergraphs. Joint work with M. Balko, J. Hubička, M. Konečný, and L. Vena, see https://arxiv.org/abs/2008.00268 Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! * * * Master defense Friday, June 18 "Aspects of Vaught's Conjecture" Michael Zechner Examining committee: Vera Fischer (Chair) Sy Friedman (Thesis Supervisor) Ben Miller (Reviewer) Time and Place Defense at 3:00pm via Moodle/BigBlueButton: This talk will be given via Moodle/BigBlueButton. If you have not received the guest link by the day before the talk, please contact richard.springer@univie.ac.at!

Reminder: Boise Extravaganza in Set Theory, June 17-19

Conference
This post is an update regarding BEST, which begins next Thursday, 17 June and runs through 17 June. We are looking forward to seeing you! You can find the list of speakers and talk titles below. The latest information will always be available on the website. BEST website: https://www.boisestate.edu/math/best/ Zoom ID 92626476913 (https://boisestate.zoom.us/j/92626476913) Plenary speakers David Fernández Bretón (UNAM). Hindman’s theorem as a weak version of the Axiom of Choice Victoria Gitman (CUNY). Characterizing large cardinals via abstract logics Jun Le Goh (Wisconsin). Inseparable pairs and recursion theory Lynne Yengulalp (Wake Forest). Completeness, G-deltas, and games Joseph Zielinski (North Texas). Orbit equivalence relations of some classes of non-locally compact Polish groups Additional speakers Filippo Calderoni (UIC). Rotation equivalence and cocycle superrigidity for compact actions Natasha Dobrinen (Denver). Big Ramsey degrees of universal inverse limit structures Thomas Gilton (Pittsburgh). Club stationary reflection and the special Aronszajn tree property Osvaldo Guzmán González (UNAM). MAD families and strategically bounding forcings Randall Holmes (Boise). An outline of a proof of the consistency of New Foundations Martina Iannella (Udine). The complexity of convex bi-embeddability among countable linear orders Krzysztof Kowitz (Gdańsk). Differentially compact space and Hindman space Maxwell Levine (Freiburg). Patterns of stationary reflection Renan Mezabarba (UFES). A characterization of productive cellularity Aristotelis Panagiotopoulos (Münster). Dynamical obstructions to classification by (co)homology and other TSI-group invariants Nick Ramsey (UCLA). Exact saturation in pseudo-elementary classes Panagiotis Rouvelas (Patras). Models of predicative NF Cory Switzer (KGRC). Tight eventually different families Riley Thornton (UCLA). Effectivization in Borel combinatorics Kameryn Williams (Hawaii). Coding sets into inner mantles Jenna Zomback (UIUC). Ergodic theorems along trees
Link to more info
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CMU logic events during coming week

Carnegie Mellon Logic Seminar

TUESDAY, June 15, 2021

Mathematical logic seminar:  3:30 P.M., Online, James Cummings, Carnegie Mellon University

Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us]
Meeting ID: 621 951 121

TITLE: Homological algebra for logicians

ABSTRACT: This is part 3 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology.

I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module).


TUESDAY, June 15, 2021

Set Theory Reading Group:  4:30 P.M., Online, James Cummings, Carnegie Mellon University

Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us]
Meeting ID: 621 951 121

TITLE: Homological algebra for logicians

ABSTRACT: This is part 4 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology.

I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module).


THURSDAY, June 17, 2021

Ph.D. Thesis Defense:  12:00 P.M., Online, Marcos Mazari-Armida

Zoom:
https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09

TITLE OF DISSERTATION: Remarks on classification theory for abstract elementary classes with applications to abelian group theory and ring theory

EXAMINERS:
Prof. Rami Grossberg (Committee Chair)
Prof. Jeremy Avigad
Prof. John Baldwin, UIC
Prof. Will Boney, Texas State
Prof. James Cummings

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Raffaella Cutolo (Università degli Studi di Napoli Federico II)
TITLE: N-Berkeley cardinals and the two futures of set theory
DATE: 9 June 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.















Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609














Talk tomorrow by Piotr Szewczak (1:30 pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Piotr Szewczak
Date and Time: Friday, June 4th, 2021 - 1:30pm to 3:00pm
Title: Abstract colorings, games and ultrafilters
Abstract: 
During the talk we consider various kinds of Ramsey-type theorems.

Bergelson and Hindman investigated finite colorings of the complete graph [N]^2 with vertices in natural numbers, involving an algebraic structure of N. It follows from their result that for each finite coloring of [N]^2, there are finite pairwise disjoint sets F1, F2, … such that each set Fn contains an arithmetic progression of length n and all edges between vertices from different sets Fn have the same color. Colorings of graphs appear also in the context of combinatorial covering properties. Scheepers proved that a set of reals X is Menger if and only if for every finite coloring of the complete graph whose vertices are open sets in X and an open omega-cover U of X (i.e., every finite subset of X is contained in a proper subset of X from the cover), there are finite pairwise disjoint subfamilies F1, F2, … of U such that the union of these families is point-infinite cover of X and all edges between vertices from different sets Fn have the same color.

The aim of the talk is to present a theorem that captures many results in a similar spirit (including mentioned above). To this end we use topological games and some special ultrafilters in the Stone—Cech compactification of semigroups. The research was motivated by the recent result of Tsaban, who extended the celebrated Hindman Finite Sum Theorem (and its high-dimensional version due to Milliken and Taylor) to covers of Menger spaces.


Ivan Ongay Valverde
ongay@yorku.ca
York University Postdoc (he/his)

Talk this Friday June 4th by Piotr Szewczak (1:30 pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Piotr Szewczak
Date and Time: Friday, June 4th, 2021 - 1:30pm to 3:00pm
Title:   Abstract colorings, games and ultrafilters
Abstract: 
During the talk we consider various kinds of Ramsey-type theorems.

Bergelson and Hindman investigated finite colorings of the complete graph [N]^2 with vertices in natural numbers, involving an algebraic structure of N. It follows from their result that for each finite coloring of [N]^2, there are finite pairwise disjoint sets F1, F2, … such that each set Fn contains an arithmetic progression of length n and all edges between vertices from different sets Fn have the same color. Colorings of graphs appear also in the context of combinatorial covering properties. Scheepers proved that a set of reals X is Menger if and only if for every finite coloring of the complete graph whose vertices are open sets in X and an open omega-cover U of X (i.e., every finite subset of X is contained in a proper subset of X from the cover), there are finite pairwise disjoint subfamilies F1, F2, … of U such that the union of these families is point-infinite cover of X and all edges between vertices from different sets Fn have the same color.

The aim of the talk is to present a theorem that captures many results in a similar spirit (including mentioned above). To this end we use topological games and some special ultrafilters in the Stone—Cech compactification of semigroups. The research was motivated by the recent result of Tsaban, who extended the celebrated Hindman Finite Sum Theorem (and its high-dimensional version due to Milliken and Taylor) to covers of Menger spaces.



Ivan Ongay Valverde
ongay@yorku.ca
York University Postdoc (he/his)

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Michał Tomasz Godziszewski  (University of Warsaw)
TITLE: The Multiverse, Recursive Saturation and Well-Foundedness Mirage
DATE: 2 June 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.














Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609













Two events on June 8

Carnegie Mellon Logic Seminar
TUESDAY, June 8, 2021 Mathematical logic seminar: 3:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Title: Homological algebra for logicians ABSTRACT: This is part 1 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module) TUESDAY, June 8, 2021 Set Theory Reading Group: 4:30 P.M., Online, James Cummings, Carnegie Mellon University Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Title: Homological algebra for logicians ABSTRACT: This is part 2 of a short series of talks aimed at giving some background for Nathaniel Bannister's forthcoming seminars. Nathaniel's talks will describe his work with Bergfalk and Moore on the additivity of strong homology. I will give a rapid overview of some necessary background in homological algebra (eg abelian categories, chain complexes, derived functors). I will assume very little background, just familiarity with basic notions in category theory (category, functor, natural transformation) and algebra (the definition of an R-module)

Talk Tomorrow by Boban Velickovic at 1 30 (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Boban Velickovic
Date and Time: Friday, May 28th, 2021 - 1:30pm to 3:00pm
Title:   Non vanishing higher derived limits 
Abstract: 
In the study of strong homology Mardesic and Prasolov isolated a certain inverse system of abelian groups A indexed by functions from \omega to \omega. 
They showed that if strong homology is additive on a class of spaces containing closed subsets of Euclidean spaces then the higher derived limits lim^n A must vanish for n >0.
They also proved that under the Continuum Hypothesis lim^1 A does not vanish. On the other hand Down, Simon and Vaughan showed that under PFA lim^1 A=0 
 The question whether lim^n A vanishes higher n has attracted considerable attention recently. First, Bergfalk shows that it was consistent lim^2 A does not vanish. 
Later Bergfalk and Lambie-Hanson showed that, assuming modest large cardinal axioms, lim^n A vanishes for all n. The large cardinal assumption was later removed by Bergfalk, Hrusak and Lambie-Hanson. We complete the picture by showing that, for any n>0, it is relatively consistent with ZFC that lim^n A is non zero. 

This is joint work with Alessandro Vignati.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk on Thursday, May 27

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, May 27 "Independent families and singular cardinals" Diana Carolina Montoya (KGRC) In this talk, we will discuss the concept of independent families for uncountable cardinals. First, we will mention a summary of results regarding the existence of such families in the case of an uncountable regular cardinal. In the second part, we focus on the singular case and present two results of ours. This is joint work with Omer Ben-Neria. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! Please note: There will be no talk in the research seminar next Thursday, June 3 (Corpus Christi).

An interesting series of talks for grad students

Toronto Set Theory Seminar
Hello everyone,

Vera Fischer is organizing a series of short talks intended for graduate students.
The idea of the talks is one short talk once a week, with the idea to
introduce some areas of set theory to the students.

Interested students should just send Vera a short email and she will add
them to the list of participants.   vera.fischer@univie.ac.at

The time is not optimal for people in the american continent time zones
(it is 9:30am CET, Fridays, May 28-June 18), but she will record the
talks for those who want to hear them at a later point. Here is
the program until the end of the semester.

https://sites.google.com/view/short-talks-logic-uni-wien/home



Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk Friday May 27th (this friday) by Boban Velickovic at 1 30 (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Boban Velickovic
Date and Time: Friday, May 28th, 2021 - 1:30pm to 3:00pm
Title:   Non vanishing higher derived limits 
Abstract: 
In the study of strong homology Mardesic and Prasolov isolated a certain inverse system of abelian groups A indexed by functions from \omega to \omega. 
They showed that if strong homology is additive on a class of spaces containing closed subsets of Euclidean spaces then the higher derived limits lim^n A must vanish for n >0.
They also proved that under the Continuum Hypothesis lim^1 A does not vanish. On the other hand Down, Simon and Vaughan showed that under PFA lim^1 A=0 
 The question whether lim^n A vanishes higher n has attracted considerable attention recently. First, Bergfalk shows that it was consistent lim^2 A does not vanish. 
Later Bergfalk and Lambie-Hanson showed that, assuming modest large cardinal axioms, lim^n A vanishes for all n. The large cardinal assumption was later removed by Bergfalk, Hrusak and Lambie-Hanson. We complete the picture by showing that, for any n>0, it is relatively consistent with ZFC that lim^n A is non zero. 

This is joint work with Alessandro Vignati.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Barcelona Set theory Seminar

Barcelona Logic Seminar


Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   David Asperó (UEA, Norwich)
TITLE: Around (*)
DATE: 26 May 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.















Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609












Barcelona Set theory Seminar

Barcelona Logic Seminar


Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   David Asperó (UEA, Norwich)
TITLE: Around (*)
DATE: 26 May 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.















Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609












Barcelona Set theory Seminar

Barcelona Logic Seminar


Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   David Asperó (UEA, Norwich)
TITLE: Around (*)
DATE: 26 May 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.















Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609












(KGRC) research seminar talk on Thursday, May 20

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, May 20 "Extensions of inner models of ZFC" Lev Bukovsky (Pavol Jozef Šafárik University in Košice, Slovakia) I would like to present some results of members of Vopěnka's seminary in 1960's and 1970's (B. Balcar, P. Vopěnka, P. Hájek and me), which were either not published or published in the language of semisets theory. Consequently, those results are not commonly known. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Luca Incurvati (Amsterdam)
TITLE: Iteration, dependence and structuralism
DATE: 19 May 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.













Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609













This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 3, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 3rd, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Graziana Ciola (Radboud Nijmegen).
Title: Marsilius of Inghen, John Buridan and the Semantics of Impossibility

Abstract: In the 14th-century, imaginable yet in some sense impossible non-entities start playing a crucial role in logic, natural philosophy and metaphysics. Throughout the later middle ages and well into early modernity, Marsilius of Inghen’s name comes to be unavoidably associated with the semantics of imaginable impossibilities in most logical and metaphysical discussions. In this paper I analyse Marsilius of Inghen’s semantic treatment of impossible referents, through a comparison with John Buridan’s. While in many ways Marsilius is profoundly influenced by Buridan’s philosophy, his semantic analysis of impossibilia is radically different from Buridan’s. Overall, Buridan tends to analyse away impossible referents in terms of complex concepts by combining possible simple individual parts. Marsilius, on the one hand, treats impossibilia as imaginable referents that are properly unitary; on the other hand, he extends the scope of his modal semantics beyond the inclusion of merely relative impossibilities, allowing for a full semantic treatment of absolute impossibilities as well. Here, I will explore the extent of these differences between Buridan’s and Marsilius of Inghen’s semantics, their presuppositions, and their respective conceptual impact on early modern philosophy of logic and mathematics.




- - - - Tuesday, May 4, 2021 - - - -



- - - - Wednesday, May 5, 2021 - - - -



- - - - Thursday, May 6, 2021 - - - -

Philog Seminar
CUNY Graduate Center
Thursday May 6, 2021, 6:30 PM
Ada Coronado
Nietzsche on, Logic, Philosophy, and Moral Values
 
Introduction: Studies in logic rarely ever mention Fredrich Nietzsche.  There is very little literature on Nietzsche’s critique of classical logic and there is no indication that he followed the developments that were occurring in the field in the 19th century by contemporaneous thinkers such as George Boole, Frege, or Augustus De Morgan.  Yet, logic is central to Nietzsche’s seminal work Beyond Good and Evil: Prelude to a Philosophy of the Future, henceforth referred to as BGE.  Believing that classical logic falsely reinforces the religious promise of absolutism and certainty, Nietzsche rejects the possibility of a priori truths qua truth, but embraces logic to the extent that he considers it the vehicle that systematically discharges a philosopher’s energy and morality onto the world.

In this talk I consider Nietzsche’s critique of moral values as they relate to his rejection of both a priori truths and the semantic principle of bivalence, or what he calls the “faith of opposite values”.  I argue that Nietzsche’s approach to philosophy, logic, and moral values heralds the future philosophical significance of multivalent systems and paraconsistent logic.

A Zoom link will be posted on  https://philog.arthurpaulpedersen.org/



- - - - Friday, May 7, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 7, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Benjamin Goodman, CUNY
Woodin's Extender Algebra

This oral exam talk will present a proof of Woodin's result that every real number is generic over some iterated ultrapower of any model with a Woodin cardinal. No fine structure theory will be used, and there will be a brief introduction to iteration trees.




Next Week in Logic at CUNY:

- - - - Monday, May 10, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 10th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Filippo Casati (Lehigh)

Title: Heidegger on the Limits and Possibilities of Human Thinking

Abstract: In my talk, I will address what Heidegger calls ‘the basic problem’ of his philosophy, that is, the alleged incompatibility between the notion of Being, our thinking, and logic. First of all, I will discuss some of the ways in which Heideggerians have dealt with this incompatibility by distinguishing what I call the irrationalist and rationalist interpretation. Secondly, I will argue that these two interpretations face both exegetical and philosophical problems. To conclude, I will defend an alternative way to address the incompatibility between the notion of Being, our thinking, and logic. I will argue that, in some of his late works, Heidegger seems to suggest that the real problem lies in the philosophical illusion that we can actually assess the limits of our thinking and, therewith, our logic. Heidegger’s philosophy, I deem, wants to free us from such a philosophical illusion by delivering an experience which reminds us that our thinking is something we can never ‘look at from above’ in order to either grasp its limits or realize that it has no limits whatsoever.




- - - - Tuesday, May 11, 2021 - - - -



- - - - Wednesday, May 12, 2021 - - - -



- - - - Thursday, May 13, 2021 - - - -

Philog Seminar
CUNY Graduate Center
Thursday May 13, 2021, 6:30 PM

Eric Pacuit, University of Maryland

Epistemic Networks for Imprecise Agents

Abstract: What is the best form for social influence to take?  Are all policies which aim to increase the amount of interaction over a particular issue likely to be successful in their aims?  In this talk, I will survey some models that have been proposed by economists and social epistemologists to address these questions. These models typically assume that the agents have precise beliefs about the proposition that they are trying to learn.  However, in many learning situations, at least some of the agents may have imprecise beliefs about the proposition that they are trying to learn.  The second part of the talk will report on some work in progress with Paul Pedersen about how best to design communication networks when some agents have imprecise beliefs.

Eric Pacuit is an associate professor in the Department of Philosophy at the University of Maryland. Prior to coming to Maryland, Eric did his graduate work at the City University of New York Graduate Center, and was a postdoctoral researcher at the Institute for Logic, Language and Computation at the University of Amsterdam and in the Departments of Philosophy and Computer Science at Stanford University. Eric’s primary research interests are in logic (especially modal logic), game theory, social choice theory, and formal and social epistemology. His research has been funded by the Natural Science Foundation and a Vidi grant from the Dutch science foundation (NWO).

A Zoom link will be posted on https://philog.arthurpaulpedersen.org/ on Wednesday




- - - - Friday, May 14, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 14, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna
Tight Maximal Eventually Different Families

Maximal almost disjoint (MAD) families and their relatives have been an important area of combinatorial and descriptive set theory since at least the 60s. In this talk I will discuss some relatives of MAD families, focussing on eventually different families of functions f:ωωf:ω→ω and eventually different sets of permutations pS(ω)p∈S(ω). In the context of MAD families it has been fruitful to consider various strengthenings of the maximality condition to obtain several flavors of 'strongly' MAD families. One such strengthening that has proved useful in recent literature is that of tightness. Tight MAD families are Cohen indestructible and come with a properness preservation theorem making them nice to work with in iterated forcing contexts.

I will introduce a version of tightness for maximal eventually different families of functions f:ωωf:ω→ω and maximal eventually different families of permutations pS(ω)p∈S(ω) respectively. These tight eventually different families share a lot of the nice, forcing theoretic properties of tight MAD families. Using them, I will construct explicit witnesses to ae=ap=1ae=ap=ℵ1 in many known models of set theory where this equality was either not known or only known by less constructive means. Working over LL we can moreover have the witnesses be Π11Π11 which is optimal for objects of size 1ℵ1 in models where CHCH fails. These results simultaneously strengthen several known results on the existence of definable maximal sets of reals which are indestructible for various definable forcing notions. This is joint work with Vera Fischer.





 Next Week in Logic at CUNY:

- - - - Monday, May 17, 2021 - - - -



- - - - Tuesday, May 18, 2021 - - - -



- - - - Wednesday, May 19, 2021 - - - -



- - - - Thursday, May 20, 2021 - - - -



- - - - Friday, May 21, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 21, 1pm
The seminar will take place virtually at 1pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Omer Ben-Neria, Hebrew University
TBA

- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Sakaé Fuchino (Kobe)
TITLE: Generically supercompact cardinals as reflection principles
DATE: 12 April 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.












Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609































All links to today talk work (preferably, use the one to fill the form)

Toronto Set Theory Seminar
Hello everyone,

Our webmaster is a magician, so any of the links I have sent will lead to the seminar talk.

Nevertheless, since the fields institute like to have general data about who attends, the following link will be the one that will lead you to the registration form and then to the talk. This is the best one to use (that, curiously, is the same as in the very first email):


That is the link that you can also find in the webpage. Thanks to Miles for his quick and awesome help.

Best

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Today (Friday, 7th) talk by Itsvan Juhasz

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and, only in case that it appears, fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance. This is the correct link.


Here the speaker information:

Speaker: Itsvan Juhasz
Date and Time: Friday, May 7th, 2021 - 1:30pm to 3:00pm
Title:  Anti-Urysohn spaces
Abstract: please see attached pdf or visit http://www.fields.utoronto.ca/talks/Anti-Urysohn-spaces

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk Tomorrow by Itsvan Juhasz at 1 30 pm (Toronto time)

Toronto Set Theory Seminar
I owe an apology to everyone. Our recurring meeting ended without me noticing, for this session we will use the following link. Most likely the registration form will not appear.

I'll talk with the webmaster to fix all the issues.

Fields Seminars 1 is inviting you to a scheduled Zoom meeting.

Topic: Set Theory Seminar
Time: 1:30-3:00 pm Friday May 7th

Join Zoom Meeting
https://zoom.us/j/97109130026?pwd=a2VMVUJBMmZweXU4a0ZnaE02NmJvZz09

Meeting ID: 971 0913 0026
Passcode: 729463
One tap mobile
+17789072071,,97109130026# Canada
+14388097799,,97109130026# Canada

Dial by your location
        +1 778 907 2071 Canada
        +1 438 809 7799 Canada
        +1 587 328 1099 Canada
        +1 647 374 4685 Canada
        +1 647 558 0588 Canada
Meeting ID: 971 0913 0026
Find your local number: https://zoom.us/u/abXb8IbMLt


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com


On Thu, May 6, 2021 at 7:00 PM Ivan Ongay Valverde <ivan.ongay.valverde@gmail.com> wrote:
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Itsvan Juhasz
Date and Time: Friday, May 7th, 2021 - 1:30pm to 3:00pm
Title:  Anti-Urysohn spaces
Abstract: please see attached pdf or visit http://www.fields.utoronto.ca/talks/Anti-Urysohn-spaces

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk Tomorrow by Itsvan Juhasz at 1 30 pm (Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Itsvan Juhasz
Date and Time: Friday, May 7th, 2021 - 1:30pm to 3:00pm
Title:  Anti-Urysohn spaces
Abstract: please see attached pdf or visit http://www.fields.utoronto.ca/talks/Anti-Urysohn-spaces

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, May 3, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 3rd, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Graziana Ciola (Radboud Nijmegen).
Title: Marsilius of Inghen, John Buridan and the Semantics of Impossibility

Abstract: In the 14th-century, imaginable yet in some sense impossible non-entities start playing a crucial role in logic, natural philosophy and metaphysics. Throughout the later middle ages and well into early modernity, Marsilius of Inghen’s name comes to be unavoidably associated with the semantics of imaginable impossibilities in most logical and metaphysical discussions. In this paper I analyse Marsilius of Inghen’s semantic treatment of impossible referents, through a comparison with John Buridan’s. While in many ways Marsilius is profoundly influenced by Buridan’s philosophy, his semantic analysis of impossibilia is radically different from Buridan’s. Overall, Buridan tends to analyse away impossible referents in terms of complex concepts by combining possible simple individual parts. Marsilius, on the one hand, treats impossibilia as imaginable referents that are properly unitary; on the other hand, he extends the scope of his modal semantics beyond the inclusion of merely relative impossibilities, allowing for a full semantic treatment of absolute impossibilities as well. Here, I will explore the extent of these differences between Buridan’s and Marsilius of Inghen’s semantics, their presuppositions, and their respective conceptual impact on early modern philosophy of logic and mathematics.




- - - - Tuesday, May 4, 2021 - - - -



- - - - Wednesday, May 5, 2021 - - - -



- - - - Thursday, May 6, 2021 - - - -

Philog Seminar
CUNY Graduate Center
Thursday May 6, 2021, 6:30 PM
Ada Coronado
Nietzsche on, Logic, Philosophy, and Moral Values
 
Introduction: Studies in logic rarely ever mention Fredrich Nietzsche.  There is very little literature on Nietzsche’s critique of classical logic and there is no indication that he followed the developments that were occurring in the field in the 19th century by contemporaneous thinkers such as George Boole, Frege, or Augustus De Morgan.  Yet, logic is central to Nietzsche’s seminal work Beyond Good and Evil: Prelude to a Philosophy of the Future, henceforth referred to as BGE.  Believing that classical logic falsely reinforces the religious promise of absolutism and certainty, Nietzsche rejects the possibility of a priori truths qua truth, but embraces logic to the extent that he considers it the vehicle that systematically discharges a philosopher’s energy and morality onto the world.

In this talk I consider Nietzsche’s critique of moral values as they relate to his rejection of both a priori truths and the semantic principle of bivalence, or what he calls the “faith of opposite values”.  I argue that Nietzsche’s approach to philosophy, logic, and moral values heralds the future philosophical significance of multivalent systems and paraconsistent logic.

A Zoom link will be posted on  https://philog.arthurpaulpedersen.org/



- - - - Friday, May 7, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 7, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Benjamin Goodman, CUNY
Woodin's Extender Algebra

This oral exam talk will present a proof of Woodin's result that every real number is generic over some iterated ultrapower of any model with a Woodin cardinal. No fine structure theory will be used, and there will be a brief introduction to iteration trees.




Next Week in Logic at CUNY:

- - - - Monday, May 10, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 10th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Filippo Casati (Lehigh)

Title: Heidegger on the Limits and Possibilities of Human Thinking

Abstract: In my talk, I will address what Heidegger calls ‘the basic problem’ of his philosophy, that is, the alleged incompatibility between the notion of Being, our thinking, and logic. First of all, I will discuss some of the ways in which Heideggerians have dealt with this incompatibility by distinguishing what I call the irrationalist and rationalist interpretation. Secondly, I will argue that these two interpretations face both exegetical and philosophical problems. To conclude, I will defend an alternative way to address the incompatibility between the notion of Being, our thinking, and logic. I will argue that, in some of his late works, Heidegger seems to suggest that the real problem lies in the philosophical illusion that we can actually assess the limits of our thinking and, therewith, our logic. Heidegger’s philosophy, I deem, wants to free us from such a philosophical illusion by delivering an experience which reminds us that our thinking is something we can never ‘look at from above’ in order to either grasp its limits or realize that it has no limits whatsoever.




- - - - Tuesday, May 11, 2021 - - - -



- - - - Wednesday, May 12, 2021 - - - -



- - - - Thursday, May 13, 2021 - - - -



- - - - Friday, May 14, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 14, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna




- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

(KGRC) research seminar talk on Thursday, May 6

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, May 6 "Absolute model companionship, the continuum problem, and forcibility" Matteo Viale (Università degli Studi di Torino, Italy) Absolute model companionship (AMC) is a strengthening of model companionship defined as follows: For a theory $T$, $T_{\exists\vee\forall}$ denotes the logical consequences of $T$ which are boolean combinations of universal sentences. $T^*$ is the AMC of $T$ if it is model complete and $T_{\exists\vee\forall}=T^*_{\exists\vee\forall}$. The theory $\mathsf{ACF}$ of algebraically closed field is the model companion of the theory $\mathsf{Fields}$ of fields but not its AMC as $\exists x(x^2+1=0)\in \mathsf{ACF}_{\exists\vee\forall}\steaminess\mathsf{Fields}_{\exists\vee\forall}$. Any model complete theory $T$ is the AMC of $T_{\exists\vee\forall}$. We use AMC to study the continuum problem and to gauge the expressive power of forcing. We show that (a definable version of) $2^{\aleph_0}=\aleph_2$ is the unique solution to the continuum problem which can be in the AMC of a \emph{partial Morleyization} of the $\in$-theory $\ZFC$ enriched with large cardinal axioms. We also show that (assuming large cardinals) forcibility overlaps with the apparently stronger notion of consistency for any mathematical problem $\psi$ expressible as a $\Pi_2$-sentence of a (very large fragment of) third order arithmetic ($\CH$, the Suslin hypothesis, the Whitehead conjecture for free groups, are a small sample of such problems $\psi$). Partial Morleyizations can be described as follows: let $F_{\tau}$ be the set of first order $\tau$-formulae; for $A\subseteq F_\tau$, $\tau_A$ is the expansion of $\tau$ adding atomic relation symbols $R_\phi$ for all formulae $\phi$ in $A$ and $T_{\tau,A}$ is the $\tau_A$-theory asserting that each $\tau$-formula $\phi(\vec{x})\in A$ is logically equivalent to the corresponding atomic formula $R_\phi(\vec{x})$. For a $\tau$-theory $T$, $T+T_{\tau,A}$ is the \emph{partial Morleyization} of $T$ induced by $A\subseteq F_\tau$. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

(KGRC) research seminar talk on Thursday, April 29

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, April 29 "Fullness and mixing property for boolean valued models" Moreno Pierobon (Università di Pisa, Italy) Besides being one of the classical approaches to forcing, boolean valued models provide a flexible tool to produce a variety of structures. In this talk, we will investigate in details the fullness property and the mixing property for boolean valued models. The former is necessary to control the semantics when quotienting a boolean valued model by an ultrafilter. The latter implies the former and it is easier to check. We will show that not every model is full, and the mixing property in not equivalent to fullness. Moreover, we will improve the classical Łoś Theorem for boolean valued models. In the end, we will give a simple characterization of the mixing property using étalé spaces. This last result is an easy corollary of a more general study we made on the categorical equivalence between boolean valued models and presheaves. This is a joint work with Matteo Viale. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 26, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 26th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Rohan French (UC Davis).
Title: Non-Classical Metatheory

Abstract: A common line of thinking has it that proponents of non-classical logics who claim that their preferred logic L gives the correct account of validity, while at the same time giving proofs of theorems about L using classical logic, are in some sense being insincere in their claim that L is the correct logic. This line of thought quite naturally motivates a correctness requirement on a non-classical logic L: that it be able to provide internally acceptable proofs of its main metatheorems. Of central importance amongst such metatheorems will typically be soundness and completeness results, such results being apt to play important roles in arguments showing that a given logic gives the correct account of validity. On the face of it this sounds like a reasonable requirement, but determining its precise content requires us to settle two important conceptual questions: what counts as a completeness proof for a logic, and what does it mean for a result to be internally acceptable? To get clearer on this issue we will look at three different results which have some claim to being internally acceptable soundness and completeness proofs, focusing for ease of comparison on the case of intuitionistic propositional logic, examining the extent to which they can be said to provide internally acceptable soundness and completeness results.





- - - - Tuesday, Apr 27, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 20, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Dave Marker, University of Illinois at Chicago
Real closures of ω1ω1-like models of PA

D'Aquino, Knight and Starchenko showed the real closure of a model of Peano Arithmetic is recursively saturated. Thus any two countable models of PA with the same standard system have isomorphic real closures. Charlie Steinhorn, Jim Schmerl and I showed that even for ω1ω1-like model of PA the situation is very different. We construct 212ℵ1 recursively saturated elementarily equivalent ω1ω1-like models of PA with the same standard system and non-isomorphic real closures.



- - - - Wednesday, Apr 28, 2021 - - - -



- - - - Thursday, Apr 29, 2021 - - - -



- - - - Friday, Apr 30, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 30, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Elliot Glazer, Harvard University

Paradoxes of perfectly small sets

We define a set of real numbers to be perfectly small if it has perfectly many disjoint translates. Such sets have a strong intuitive claim to being probabilistically negligible, yet no non-trivial measure assigns them all a value of 0. We will prove from a moderate amount of choice that any total extension of Lebesgue measure concentrates on a perfectly small set, suggesting that for any such measure, translation-invariance fails 'as badly as possible.' From the ideas of this proof, we will also derive analogues of well-known paradoxes of randomness, specifically Freiling's symmetry paradox and the infinite prisoner hat puzzle, in terms of perfectly small sets. Finally, we discuss how these results constrain what a paradox-free set theory can look like and some related open questions.






Next Week in Logic at CUNY:

- - - - Monday, May 3, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, May 3rd, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Graziana Ciola (Radboud Nijmegen).
Title: Marsilius of Inghen, John Buridan and the Semantics of Impossibility

Abstract: In the 14th-century, imaginable yet in some sense impossible non-entities start playing a crucial role in logic, natural philosophy and metaphysics. Throughout the later middle ages and well into early modernity, Marsilius of Inghen’s name comes to be unavoidably associated with the semantics of imaginable impossibilities in most logical and metaphysical discussions. In this paper I analyse Marsilius of Inghen’s semantic treatment of impossible referents, through a comparison with John Buridan’s. While in many ways Marsilius is profoundly influenced by Buridan’s philosophy, his semantic analysis of impossibilia is radically different from Buridan’s. Overall, Buridan tends to analyse away impossible referents in terms of complex concepts by combining possible simple individual parts. Marsilius, on the one hand, treats impossibilia as imaginable referents that are properly unitary; on the other hand, he extends the scope of his modal semantics beyond the inclusion of merely relative impossibilities, allowing for a full semantic treatment of absolute impossibilities as well. Here, I will explore the extent of these differences between Buridan’s and Marsilius of Inghen’s semantics, their presuppositions, and their respective conceptual impact on early modern philosophy of logic and mathematics.




- - - - Tuesday, May 4, 2021 - - - -



- - - - Wednesday, May 5, 2021 - - - -



- - - - Thursday, May 6, 2021 - - - -



- - - - Friday, May 7, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, May 7, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Benjamin Goodman, CUNY




- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Yair Hayut (Hebrew University, Jerusalem)
TITLE: omega-strongly measurable cardinals
DATE: 28 April 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.











Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609





























Two CMU events on Tuesday, April 27

Carnegie Mellon Logic Seminar
TUESDAY, April 27, 2021 Mathematical logic seminar: 3:30 P.M., Online, Omer Ben-Neria, The Hebrew University of Jerusalem Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Tree-like scales and free subsets of set theoretic algebras, part 1 ABSTRACT: In his PhD thesis, Luis Pereira isolated and developed several principles of singular cardinals that emerge from Shelah's PCF theory; principles which involve properties of scales, such as the inexistence of continuous Tree Like scales, and properties of internally approachable structures such as the Approachable Free Subset Property. In the first talk, I will discuss these principles and their relations, and present new results from a joint work with Dominik Adolf concerning their consistency and consistency strength. The second talk will focus on the extender-based Prikry forcing and its connection with these principles. TUESDAY, April 27, 2021 Set Theory Reading Group: 4:30 P.M., Online, Omer Ben-Neria, The Hebrew University of Jerusalem Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Tree-like scales and free subsets of set theoretic algebras, part 2 ABSTRACT: In his PhD thesis, Luis Pereira isolated and developed several principles of singular cardinals that emerge from Shelah's PCF theory; principles which involve properties of scales, such as the inexistence of continuous Tree Like scales, and properties of internally approachable structures such as the Approachable Free Subset Property. In the first talk, I will discuss these principles and their relations, and present new results from a joint work with Dominik Adolf concerning their consistency and consistency strength. The second talk will focus on the extender-based Prikry forcing and its connection with these principles.

(KGRC) research seminar talk on Thursday, April 22

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, April 22 "MAD families and strategically bounding forcings" Osvaldo Guzmán (Universidad Nacional Autónoma de México) The notion of strategically bounding forcings is a natural game-theoretic strengthening of the bounding property for partial orders. In this talk, we will study the basic properties of strategically bounding forcings and talk about indestructibility of MAD families. The motivation for this work is the problem of Roitman. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 19, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 19th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
V. Alexis Peluce (CUNY)
Title: Brouwer’s First Act of Intuitionism

Abstract: L.E.J. Brouwer famously argued that mathematics was completely separated from formal language. His explanation for why this is so leaves room for interpretation. Indeed, one might ask: what sort of philosophical background is required to make sense of the strong anti-linguistic views of Brouwer? In this talk, we outline some possible answers to the above. We then present an interpretation that we argue best makes sense of Brouwer’s first act.






- - - - Tuesday, Apr 20, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 20, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Cordón Franco Universidad de Sevilla

Induction and collection up to definable elements: calibrating the strength of parameter-free ΔnΔn-minimization.

In this talk we shall deal with fragments of first-order Peano Arithmetic obtained by restricting the conclusion of the induction or the collection axiom to elements in a prescribed subclass DD of the universe. Fix n>0n>0. The schemes of ΣnΣn-induction up to ΣmΣm-definable elements and the schemes of ΣnΣn-collection up to ΣmΣm-definable elements form two families of subtheories of IΣnIΣn and BΣnBΣn, respectively, obtained in this way.

The properties of ΣnΣn-induction up to ΣmΣm-definable elements for nmn≥m are reasonably well understood and interesting applications of these fragments are known. However, an analysis of the case n<mn<m was pending. In the first part of this talk, we address this problem and show that it is related to the following general question: 'Under which conditions on a model MM can we prove that every non-empty ΣmΣm-definable subset of MM contains some ΣmΣm-definable element?'

In the second part of the talk, we show that, for each n1n≥1, the scheme of ΣnΣn-collection up to ΣnΣn-definable elements provides us with an axiomatization of the Σn+1Σn+1-consequences of BΣnBΣn. As an application, we obtain that BΣnBΣn is Σn+1Σn+1-conservative over parameter-free ΔnΔn-minimization (plus IΣn1n−1), thus partially answering a question of R. Kaye.

This is joint work with F.Félix Lara-Martín (University of Seville).



- - - - Wednesday, Apr 21, 2021 - - - -



- - - - Thursday, Apr 22, 2021 - - - -

Philog Seminar
Thursday, April 22, 2021, 6:30 PM
Todd Stambaugh (John Jay)
Knowledge, behavior, and rationality: Rationalizability in epistemic games

Abstract:  In strategic situations, agents base actions on knowledge and beliefs.  This  includes  knowledge  about  others’  strategies  and  preferences  over strategy profiles, but also about other external factors. Bernheim  and  Pearce  in  1984  independently  defined  the  game  theoretic solution concept of rationalizability, which is built on the premise that rational agents will only take actions that are the best response to some situation that they  consider  possible. 

This  accounts  for  other  agents’  rationality  as  well, limiting  the  strategies  to  which  a  particular  agent  must  respond,  enabling further elimination until the strategies stabilize. We seek to generalize rationalizability to account not only for actions, but knowledge of the world as well. This will enable us to examine the interplay between  action  based  and  knowledge  based  rationality. 

We  give  an  account of what it means for an action to be rational relative to a particular state of affairs, and in turn relative to a state of knowledge. We  present  a  class  of  games,  Epistemic  Messaging  Games  (EMG),  with a  communication  stage  that  clarifies  the  epistemic  state  among  the  players prior  to  the  players’  actions.  We  use  a  history  based  model,  which  frames individual  knowledge  in  terms  of  local  projections  of  a  global  history.  With this framework, we give an account of rationalizability for subclasses of EMG

(Joint work with Rohit Parikh.  Todd Stambaugh received his doctorate in 2018, from the mathematics program of CUNY).

A Zoom link will be posted on philog.arthurpaulpedersen.org on Wednesday




- - - - Friday, Apr 23, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Andrés Villaveces, Universidad Nacional de Colombia – Bogotá
Two logics, and their connections with large cardinals / Questions for BDGM: Part II

In the past couple of years I have been involved (joint work with Väänänen and independently with Shelah) with some logics in the vicinity of Shelah's L1κLκ1 (a logic from 2012 that has Interpolation and a very weak notion of compactness, namely Strong Undefinability of Well-Orderings, and in some cases has a Lindström-type theorem for those two properties). Our work with Väänänen weakens the logic but keeps several properties. Our work with Shelah explores the connection with definability of AECs.

These logics seem to have additional interesting properties under the further assumption of strong compactness of a cardinal, and this brings them close to recent work of Boney, Dimopoulos, Gitman and Magidor [BDGM].

During the first lecture, I plan to describe two games and a syntax of two logics: Shelah's L1κLκ1 and my own logic (joint work with Väänänen) L1,cκLκ1,c. I will stress some of the properties of these logics, without any use of large cardinal assumptions.

During the second lecture, I plan to enter rather uncharted territory. I will describe some constructions done by Shelah (mostly) under the assumption of strong compactness, but I also plan to bring these logics to a territory closer to the work of [BDGM]. This second lecture will have more conjectures, ideas, and (hopefully interesting) discussions with some of the authors of that paper.



Next Week in Logic at CUNY:

- - - - Monday, Apr 26, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 26th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Rohan French (UC Davis).
Title: Non-Classical Metatheory

Abstract: A common line of thinking has it that proponents of non-classical logics who claim that their preferred logic L gives the correct account of validity, while at the same time giving proofs of theorems about L using classical logic, are in some sense being insincere in their claim that L is the correct logic. This line of thought quite naturally motivates a correctness requirement on a non-classical logic L: that it be able to provide internally acceptable proofs of its main metatheorems. Of central importance amongst such metatheorems will typically be soundness and completeness results, such results being apt to play important roles in arguments showing that a given logic gives the correct account of validity. On the face of it this sounds like a reasonable requirement, but determining its precise content requires us to settle two important conceptual questions: what counts as a completeness proof for a logic, and what does it mean for a result to be internally acceptable? To get clearer on this issue we will look at three different results which have some claim to being internally acceptable soundness and completeness proofs, focusing for ease of comparison on the case of intuitionistic propositional logic, examining the extent to which they can be said to provide internally acceptable soundness and completeness results.





- - - - Tuesday, Apr 27, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 20, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Dave Marker, University of Illinois at Chicago
Real closures of ω1ω1-like models of PA

D'Aquino, Knight and Starchenko showed the real closure of a model of Peano Arithmetic is recursively saturated. Thus any two countable models of PA with the same standard system have isomorphic real closures. Charlie Steinhorn, Jim Schmerl and I showed that even for ω1ω1-like model of PA the situation is very different. We construct 212ℵ1 recursively saturated elementarily equivalent ω1ω1-like models of PA with the same standard system and non-isomorphic real closures.



- - - - Wednesday, Apr 28, 2021 - - - -



- - - - Thursday, Apr 29, 2021 - - - -



- - - - Friday, Apr 30, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 30, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Elliot Glazer, Harvard University

- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Sam Roberts (Universität Konstanz)
TITLE: Reinhardt’s potentialism
DATE: 21 April 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.












Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609





























Tomorrow talk by Micheal Hrusak (1:30 pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Micheal Hrusak
Date and Time: Friday, April 16th, 2021 - 1:30pm to 3:00pm
Title:  Ultrafiters, MAD families and the Kat\v{e}tov order
Abstract: We shall survey recent results concerning classification of MAD
families and ultrafilters using the Kat\v{e}tov order, concentrating on
open problems.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Friday 16th talk by Micheal Hrusak (1:30 pm Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Micheal Hrusak
Date and Time: Friday, April 16th, 2021 - 1:30pm to 3:00pm
Title:  Ultrafiters, MAD families and the Kat\v{e}tov order
Abstract: We shall survey recent results concerning classification of MAD
families and ultrafilters using the Kat\v{e}tov order, concentrating on
open problems.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk on Thursday, April 15

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, April 15 "Choice, Groups, and Topoi" Andreas Blass (University of Michigan) Work of Tarski, Mostowski, Gauntt, and Truss provides finite, group-theoretic criteria for ZF-provability of implications between weak choice axioms of the form "every family of n-element sets has a choice function" or "every countable family of n-element sets has a choice function." From a sufficiently broad, category-theoretic viewpoint, these implications and the equivalent group-theoretic criteria look like exactly the same statements but interpreted in different categories, namely certain particular sorts of topoi. The main result is that this equivalence applies not only to these particular sorts of topoi but to all topoi. I plan to describe the ingredients of this work --- choice principles, group properties, and topoi --- and, if time permits, give a hint about the ideas in the proofs. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Two talks on Tuesday, April 20

Carnegie Mellon Logic Seminar
TUESDAY, April 20, 2021 Mathematical logic seminar: 3:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Large cardinals and determinacy when all sets are universally Baire ABSTRACT: The large cardinal strength of the Axiom of Determinacy when enhanced with the hypothesis that all sets of reals are universally Baire is known to be much stronger than the Axiom of Determinacy itself. In fact, Sargsyan conjectured it to be as strong as the existence of a cardinal that is both a limit of Woodin cardinals and a limit of strong cardinals. Larson, Sargsyan and Wilson showed that this would be optimal via a generalization of Woodin's derived model construction. After a gentle introduction to the connection between determinacy axioms and large cardinals we will sketch a proof of Sargsyan's conjecture. TUESDAY, April 20, 2021 Set Theory Reading Group: 4:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: The exact consistency strength of "AD + all sets are universally Baire" ABSTRACT: In this second talk, we will outline the proof of Sargsyan's conjecture with more details. In particular, we will discuss a new translation procedure for hybrid mice extending work of Steel, Zhu and Sargsyan that is crucial in the construction of a model with a cardinal that is both a limit of Woodin cardinals and a limit of strong cardinals from a model of the Axiom of Determinacy in which all sets of reals are universally Baire.

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
Hi everyone,

Additional details have been added for this Thursday's talk by Joe Halpern in the Philog Seminar.

Best,
Jonas


This Week in Logic at CUNY:

- - - - Monday, Apr 12, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 12th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
William Nava (NYU)
Title: Logical deducibility and substitution in Bolzano (and beyond)

Abstract: Bolzano is famously responsible for an influential substitutional account of logical consequence (or, as he calls it, logical deducibility): a proposition, 𝜑, is logically deducible from a set of propositions, Γ, iff every uniform substitution of non-logical ideas in Γ∪{𝜑} that makes every proposition in Γ true also makes 𝜑 true. There are two problems with making sense of Bolzano’s proposal, however. One is that Bolzano argues that every proposition is of the form a has B—in other words, is a monadic atomic predication. So, for Bolzano, logically complex propositions like ‘𝜑 and 𝜓’ cannot have the semantic structure they appear to. This can be addressed, roughly, by taking complex propositions to predicate logical ideas of collections of propositions. But this introduces the second problem: for Bolzano, familiar logical ideas like ‘and’, ‘or’, and ‘not’ are complex ideas with compositional structure. I’ll show that, as a result of this structure, we cannot use the simple and familiar notion of uniform substitution in order to understand logical deducibility. We must instead use what I’ll call form-sensitive substitution. I will end by drawing some general lessons about substitutional definitions of logical consequence in languages with the resources to generate complex predicates of propositions.





- - - - Tuesday, Apr 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 13, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Roman Kossak, CUNY
Automorphisms, Jónsson Models, and Satisfaction Classes

25 years ago I wrote a paper on four open problems concerning recursively saturated models of PA. The problems are still open. I will talk about two of them: (1) Let M be a countable recursively saturated model of PA. Can every automorphism of M be extended to some recursively saturated elementary end extension of M? (2) Is there a recursively saturated model of PA that has no recursively saturated elementary submodel of the same cardinality as the model? I will present some partial results involving partial inductive satisfaction classes.






- - - - Wednesday, Apr 14, 2021 - - - -



- - - - Thursday, Apr 15, 2021 - - - -

Philog Seminar
Thursday, April 15, 6:30 PM
Joe Halpern, Cornell University
Actual Causality: A Survey

What does it mean that an event C ``actually caused'' event E?
The problem of defining actual causation goes beyond mere philosophical
speculation.  For example, in many legal arguments, it is precisely what
needs to be established in order to determine responsibility. (What exactly
was the actual cause of the car accident or the medical problem?)
The philosophy literature has been struggling with the problem
of defining causality since the days of Hume, in the 1700s.
Many of the definitions have been couched in terms of counterfactuals.
(C is a cause of E if, had C not happened, then E would not have happened.)
In 2001, Judea Pearl and I introduced a new definition of actual cause,
using Pearl's notion of structural equations to model
counterfactuals.  The definition has been revised twice since then,
extended to deal with notions like "responsibility" and "blame", and
applied in databases and program verification.  I survey
the last 15 years of work here, including joint work
with Judea Pearl, Hana Chockler, and Chris Hitchcock.  The talk will be
completely self-contained.

A Zoom link will be posted on April 14 on https://philog.arthurpaulpedersen.org/ 




- - - - Friday, Apr 16, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 16, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Villaveces CUNY



Next Week in Logic at CUNY:

- - - - Monday, Apr 19, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 19th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
V. Alexis Peluce (CUNY)
Title: Brouwer’s First Act of Intuitionism

Abstract: L.E.J. Brouwer famously argued that mathematics was completely separated from formal language. His explanation for why this is so leaves room for interpretation. Indeed, one might ask: what sort of philosophical background is required to make sense of the strong anti-linguistic views of Brouwer? In this talk, we outline some possible answers to the above. We then present an interpretation that we argue best makes sense of Brouwer’s first act.






- - - - Tuesday, Apr 20, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 20, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Cordón Franco Universidad de Sevilla



- - - - Wednesday, Apr 21, 2021 - - - -



- - - - Thursday, Apr 22, 2021 - - - -



- - - - Friday, Apr 23, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Villaveces CUNY




- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Logic Seminar 14 April 2021 17:00 hrs by Karen Seidel, HPI, University of Potsdam

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 14 April 2020, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Karen Seidel Title: Learning from informant URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Learning from positive and negative information, so called informant, is one of the models for human and machine learning introduced by Gold. We review existing classical and recent results regarding the learning power of associated settings.

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Erin Carmody (Fordham University)
TITLE: The relationships between measurable and strongly compact cardinals
DATE: 14 April 2021
TIME: 16:00 (CEST)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.











Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
























This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 12, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 12th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
William Nava (NYU)
Title: Logical deducibility and substitution in Bolzano (and beyond)

Abstract: Bolzano is famously responsible for an influential substitutional account of logical consequence (or, as he calls it, logical deducibility): a proposition, 𝜑, is logically deducible from a set of propositions, Γ, iff every uniform substitution of non-logical ideas in Γ∪{𝜑} that makes every proposition in Γ true also makes 𝜑 true. There are two problems with making sense of Bolzano’s proposal, however. One is that Bolzano argues that every proposition is of the form a has B—in other words, is a monadic atomic predication. So, for Bolzano, logically complex propositions like ‘𝜑 and 𝜓’ cannot have the semantic structure they appear to. This can be addressed, roughly, by taking complex propositions to predicate logical ideas of collections of propositions. But this introduces the second problem: for Bolzano, familiar logical ideas like ‘and’, ‘or’, and ‘not’ are complex ideas with compositional structure. I’ll show that, as a result of this structure, we cannot use the simple and familiar notion of uniform substitution in order to understand logical deducibility. We must instead use what I’ll call form-sensitive substitution. I will end by drawing some general lessons about substitutional definitions of logical consequence in languages with the resources to generate complex predicates of propositions.





- - - - Tuesday, Apr 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 13, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Roman Kossak, CUNY
Automorphisms, Jónsson Models, and Satisfaction Classes

25 years ago I wrote a paper on four open problems concerning recursively saturated models of PA. The problems are still open. I will talk about two of them: (1) Let M be a countable recursively saturated model of PA. Can every automorphism of M be extended to some recursively saturated elementary end extension of M? (2) Is there a recursively saturated model of PA that has no recursively saturated elementary submodel of the same cardinality as the model? I will present some partial results involving partial inductive satisfaction classes.






- - - - Wednesday, Apr 14, 2021 - - - -



- - - - Thursday, Apr 15, 2021 - - - -

Philog Seminar
Thursday, April 8, 6:30 PM
Speaker: Joseph Halpern, Cornell




- - - - Friday, Apr 16, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 16, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Villaveces CUNY



Next Week in Logic at CUNY:

- - - - Monday, Apr 19, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 19th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
V. Alexis Peluce (CUNY)
Title: Brouwer’s First Act of Intuitionism

Abstract: L.E.J. Brouwer famously argued that mathematics was completely separated from formal language. His explanation for why this is so leaves room for interpretation. Indeed, one might ask: what sort of philosophical background is required to make sense of the strong anti-linguistic views of Brouwer? In this talk, we outline some possible answers to the above. We then present an interpretation that we argue best makes sense of Brouwer’s first act.






- - - - Tuesday, Apr 20, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 20, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Cordón Franco Universidad de Sevilla



- - - - Wednesday, Apr 21, 2021 - - - -



- - - - Thursday, Apr 22, 2021 - - - -



- - - - Friday, Apr 23, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Villaveces CUNY




- - - - Other Logic News - - - -






- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Unusual time for tomorrow talk by Joerg Brendle (10:30 am Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time and please notice the UNUSUAL TIME.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Joerg Brendle
Date and Time: Friday, April 9th, 2021 - 10:30am to 12:00pm
Title: Combinatorics of ultrafilters on complete Boolean algebras
Abstract:
The combinatorial structure of ultrafilters on the natural numbers has been investigated intensively for many decades, and a lot is known about the order structure of such ultrafilters (under either the Tukey or the Rudin-Keisler ordering), about special classes of ultrafilters (like P-points),or about cardinal invariants related to ultrafilters (like the ultrafilter number). Yet, very little has beendone so far concerning combinatorial aspects of ultrafilters on general Boolean algebras, and thepurpose of this talk will be to present some basic results in this direction.

Focus will be put on the Tukey ordering, on (non)existence of non-Tukey-maximal ultrafilters, on ultrafilter numbers, and on an analogue of the Rudin-Keisler ordering in the context of complete Boolean algebras. We will in particular deal with Cohen and random algebras. This is joint work with Francesco Parente.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Unusual time for Friday 9th talk by Joerg Brendle (10:30 am Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time and please notice the UNUSUAL TIME.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Joerg Brendle
Date and Time: Friday, April 9th, 2021 - 10:30am to 12:00pm
Title: Combinatorics of ultrafilters on complete Boolean algebras
Abstract:
The combinatorial structure of ultrafilters on the natural numbers has been investigated intensively for many decades, and a lot is known about the order structure of such ultrafilters (under either the Tukey or the Rudin-Keisler ordering), about special classes of ultrafilters (like P-points),or about cardinal invariants related to ultrafilters (like the ultrafilter number). Yet, very little has beendone so far concerning combinatorial aspects of ultrafilters on general Boolean algebras, and thepurpose of this talk will be to present some basic results in this direction.

Focus will be put on the Tukey ordering, on (non)existence of non-Tukey-maximal ultrafilters, on ultrafilter numbers, and on an analogue of the Rudin-Keisler ordering in the context of complete Boolean algebras. We will in particular deal with Cohen and random algebras. This is joint work with Francesco Parente.

Best

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Apr 5, 2021 - - - -

Logic and Metaphysics Workshop
Spring 2021
Date: Monday, April 5th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu 
Speakers: Federico Pailos and Eduardo Barrio (Buenos Aires)
Title: A Metainferential Solution to the Adoption Problem 

Abstract: In ‘The Question of Logic’ (Kripke 2020) and “The Adoption Problem and the Epistemology of Logic” (Padró 2020), Kripke and Padró argue against the possibility of adopting an alternative logic. Without having already endorsed a logic, it is not possible to derive the consequences of an alternative system. In particular, without Modus Ponens in the metatheory, one could not adopt any inferential rule at all. This seems to cause trouble for logics like LP, that does not validate this rule. Modus Ponens is a self-governing rule that cannot be adopted and could not be rejected. This is connected with the problem of the tortoise reasoner (Scambler 2019) and the problem of the tortoise Logic (Priest 2021). In this talk, we offer a new solution. With the metainferential logic TS/LP it is possible to model metalogical Modus Ponens-like reasoning while still rejecting Modus Ponens.



- - - - Tuesday, Apr 6, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 6, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Zachiri McKenzie

Topless powerset preserving end-extensions and rank-extensions of countable models of set theory

This talk will report on ongoing work that is being done in collaboration with Ali Enayat (University of Gothenburg).

For models of set theory NN and MMNN is a powerset preserving end-extension of MM if NN is an end-extension of MM and NN contains no new subsets of sets in MM. A model of Kripke-Platek Set Theory, NN, is a rank-extension of a model of Kripke-Platek Set Theory, MM, if NN is an end-extension of MM and all of the new sets in NN have rank that exceeds the rank of all of the sets in MM. A powerset preserving end-extension (rank-extension) NN of MM is topless if MNMN and there is no set in NMNM containing only sets from MM. If M=M,EMM=⟨M,EM is a model of set theory, then the admissible cover of MMCovMCovM, is defined to be the smallest admissible structure with MM forming its urelements and whose language contains a unary function function symbol, FF, that sends each mMm∈M to the set {xMxEMm}{x∈M∣xEMm}. Barwise has shown that if MM is a model of Kripke-Platek Set Theory, then CovMCovM exists and its minimality facilitates compactness arguments for infinitary languages coded in CovMCovM. We extend Barwise's analysis by showing that if MM satisfies enough set theory then the expansion of CovMCovM obtained by adding the powerset function remains admissible. This allows us to build powerset preserving end-extensions and rank-extensions of countable models of certain subsystems of ZFCZFC satisfying any given recursive subtheory of the model being extended. In particular, we show that

  1. Every countable model of KPPKPP has a topless rank-extension that satisfies KPPKPP.
  2. Every countable ωω-standard model of MOST+Π1-collectionMOST+Π1-collection has a topless powerset preserving end-extension that satisfies MOST+Π1-collectionMOST+Π1-collection.





- - - - Wednesday, Apr 7, 2021 - - - -



- - - - Thursday, Apr 8, 2021 - - - -

Philog Seminar
Thursday, April 8, 6:30 PM
Speaker: Jongjin (JJ) Kim (Korea University)

Abstract.  We discuss two approaches to life: presentism and futurism. We locate presentism within various elements of Buddhism, in the form of advice to live in the present and not to allow the future to hinder us from living in the ever present now. By contrast, futurism, which we identify with Karl Popper, advises us to think of future consequences before we act, and to act now for a better future. Of course, with its emphasis on a well-defined path to an ideal future ideally culminating in enlightenment, Buddhism undoubtedly has elements of futurism as well. We do not intend to determine which of these two approaches to time is more dominant in Buddhism, nor how the two approaches are best understood within Buddhism; but simply we intend to compare and contrast these two approaches, using those presentist elements of Buddhism as representative of presentism while contrasting them with those elements of futurism to be found in Popper and others. We will discuss various aspects of presentism and futurism, such as Ruth Millikan’s Popperian animal, the psychologist Howard Rachlin’s social and temporal discounting, and even the popular but controversial idea, YOLO (you only live once). The primary purpose of this paper is to contrast one with the other. The central question of ethics is: How should one live? Our variation on that question is: When should one live? We conjecture that the notion of flow, developed by Csikszentmihalyi, may be a better optimal choice between these two positions.

Jongjin Kim received his doctorate in Philosophy from CUNY in 2019.

For Zoom link please go to https://philog.arthurpaulpedersen.org/
on Wednesday




- - - - Friday, Apr 9, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Sandra Müller, University of Vienna
The exact consistency strength of 'AD + all sets are universally Baire'

The large cardinal strength of the Axiom of Determinacy when enhanced with the hypothesis that all sets of reals are universally Baire is known to be much stronger than the Axiom of Determinacy itself. In fact, Sargsyan conjectured it to be as strong as the existence of a cardinal that is both a limit of Woodin cardinals and a limit of strong cardinals. Larson, Sargsyan and Wilson showed that this would be optimal via a generalization of Woodin’s derived model construction. We will discuss a new translation procedure for hybrid mice extending work of Steel, Zhu and Sargsyan and use this to prove Sargsyan’s conjecture.






Next Week in Logic at CUNY:

- - - - Monday, Apr 12, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, April 5th, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
William Nava (NYU)
Title: Logical deducibility and substitution in Bolzano (and beyond)

Abstract: Bolzano is famously responsible for an influential substitutional account of logical consequence (or, as he calls it, logical deducibility): a proposition, 𝜑, is logically deducible from a set of propositions, Γ, iff every uniform substitution of non-logical ideas in Γ∪{𝜑} that makes every proposition in Γ true also makes 𝜑 true. There are two problems with making sense of Bolzano’s proposal, however. One is that Bolzano argues that every proposition is of the form a has B—in other words, is a monadic atomic predication. So, for Bolzano, logically complex propositions like ‘𝜑 and 𝜓’ cannot have the semantic structure they appear to. This can be addressed, roughly, by taking complex propositions to predicate logical ideas of collections of propositions. But this introduces the second problem: for Bolzano, familiar logical ideas like ‘and’, ‘or’, and ‘not’ are complex ideas with compositional structure. I’ll show that, as a result of this structure, we cannot use the simple and familiar notion of uniform substitution in order to understand logical deducibility. We must instead use what I’ll call form-sensitive substitution. I will end by drawing some general lessons about substitutional definitions of logical consequence in languages with the resources to generate complex predicates of propositions.





- - - - Tuesday, Apr 13, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 13, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Roman Kossak, CUNY
Automorphisms, Jónsson Models, and Satisfaction Classes

25 years ago I wrote a paper on four open problems concerning recursively saturated models of PA. The problems are still open. I will talk about two of them: (1) Let M be a countable recursively saturated model of PA. Can every automorphism of M be extended to some recursively saturated elementary end extension of M? (2) Is there a recursively saturated model of PA that has no recursively saturated elementary submodel of the same cardinality as the model? I will present some partial results involving partial inductive satisfaction classes.






- - - - Wednesday, Apr 14, 2021 - - - -



- - - - Thursday, Apr 15, 2021 - - - -



- - - - Friday, Apr 16, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 16, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andrés Villaveces CUNY


- - - - Other Logic News - - - -

Conference announcement: Boise Extravaganza in Set Theory (BEST) June 17-20
 
The 2021 Boise Extravaganza in Set Theory will take place in Zoomland during June 17-20. We would be delighted if you will attend! (Please follow https://www.boisestate.edu/math/best for future updates.)

We are currently welcoming applications to speak at BEST from researchers in set theory and related fields. We hope to receive your application by May 1, but we will continue accepting applications as long as there is space. To apply please send your name, institution, career status (and if student, advisor name), talk title, and abstract to best@boisestate.edu.



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Farmer Schlutzenberg (Muenster)
TITLE: Some results on restricted mantles
DATE: 7 April 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.









Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609


















Logic Seminar 7 April 2021 17:00 hrs at NUS by Frank Stephan

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 7 April 2020, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Frank Stephan Title: On Trees without Hyperimmune Branches URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html In the year 2013, Keng Meng Ng, Frank Stephan, Yue Yang and Liang Yu published the paper "Computational Aspects of the Hyperimmune-free Degrees" and one of the results was given without a proof. The current talk gives the full proof of this result. In particular, the talk provides the full details of the construction of an co-r.e.\ infinite binary tree with uncountablly many branches which are all hyperimmune-free, Schnorr-trivial, jump traceable, generalised low and of minimal Turing degree. Hyperimmune-free means that every function Turing reducible to it is majorised by a recursive function. Jump traceable means that for every e one can compute an explicit bound on the number of elements which some further set also depending on e enumerates and that finite set contains the Jump value at e. Generalised low means that the jump of A is recursive in the join of A and K. A minimal Turing degree is a nonrecursive Turing degree below which is only the recursive one. Schnorr trivial means that for every f truth-table reducible to the set there is a recursive function which lists out for each input x a set of x+1 many values with one of them being f(x). The slides of the quite technical talk are here: http://www.comp.nus.edu.sg/~fstephan/hiftree2021slides.ps , http://www.comp.nus.edu.sg/~fstephan/hiftree2021slides.pdf . As at least two of the authors of the paper are regular participants of the logic seminar, this is also an opportunity to present to them the full details of the proof.

Logic Seminar Tomorrow in Singapore

NUS Logic Seminar
Hello, this is a reminder on tomorrow's logic seminar. I also attach the handout of the speaker for the logic seminar (the date is 31 March 2021, 17:00 hrs Singapore time = 11:00 hrs Central European Summer Time). The handout is also linked to the logic seminar entry for the talk. See you then. Best regards, Frank Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 31 March 2021, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Lars Kristiansen, University of Oslo Title: Classic representations of irrational numbers seen from a computability and complexity-theoretic perspective. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: We will address the following question: Do we need, or do we not need, unbounded search in order to convert one representation of an irrational number into another representation? We will consider well known representations like Cauchy sequences, Dedekind cuts, base-2 expansions, base-10 expansions and continued fractions, and maybe a few less well-know representations.

Logic Seminar Wednesday 31 March 2021

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 31 March 2021, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Lars Kristiansen, University of Oslo Title: Classic representations of irrational numbers seen from a computability and complexity-theoretic perspective. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: We will address the following question: Do we need, or do we not need, unbounded search in order to convert one representation of an irrational number into another representation? We will consider well known representations like Cauchy sequences, Dedekind cuts, base-2 expansions, base-10 expansions and continued fractions, and maybe a few less well-know representations.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 29, 2021 - - - -



- - - - Tuesday, Mar 30, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 30, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Paola d’Aquino, Università della Campania -“L. Vanvitelli”
Residue rings of models of Peano Arithmetic

I will present an axiomatization of a class of residue rings of models of PA. This is obtained using valuation theory and results on models of PA. (Joint work with A. Macintyre)






- - - - Wednesday, Mar 31, 2021 - - - -



- - - - Thursday, Apr 1, 2021 - - - -



- - - - Friday, Apr 2, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 2, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Monroe Eskew University of Vienna

The approximation property and generic embeddings

The approximation property was introduced by Hamkins for his Gap Forcing Theorem, and it has turned out to be a very useful notion, appearing for example in the partial equiconsistency result of Viale and Weiss on PFA, and in the proof of Woodin's HOD Dichotomy Theorem. In the context of generic embeddings, there can be a useful interplay between elementarity and approximation. We discuss some recent work in this direction: (1) tensions between saturated ideals on ω2ω2 and the tree property (with Sean Cox), (2) fragility of the strong independence spectra (with Vera Fischer), and (3) mutual inconsistency of Foreman‘s minimal generic hugeness axioms.




Next Week in Logic at CUNY:

- - - - Monday, Apr 5, 2021 - - - -



- - - - Tuesday, Apr 6, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, April 6, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Zachiri McKenzie
TBA





- - - - Wednesday, Apr 7, 2021 - - - -



- - - - Thursday, Apr 8, 2021 - - - -



- - - - Friday, Apr 9, 2021 - - - -





- - - - Other Logic News - - - -

Conference announcement: Boise Extravaganza in Set Theory (BEST) June 17-20
 
The 2021 Boise Extravaganza in Set Theory will take place in Zoomland during June 17-20. We would be delighted if you will attend! (Please follow https://www.boisestate.edu/math/best for future updates.)

We are currently welcoming applications to speak at BEST from researchers in set theory and related fields. We hope to receive your application by May 1, but we will continue accepting applications as long as there is space. To apply please send your name, institution, career status (and if student, advisor name), talk title, and abstract to best@boisestate.edu.



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Unusual time for tomorrow talk by Sakaé Fuchino (10:30 am Toronto time)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time and please notice the UNUSUAL TIME.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Sakaé Fuchino
Date and Time: Friday, March 26th, 2021 - 10:30am to 12:00pm
Title: Laver-generically large cardinal and the Continuum Problem
Abstract:
Let us call a class $\calP$ of posets iterable, if, for any $\poP\in\calP$ and $\calP$-name
$\utpoQ$\vspace{-0.5\smallskipamount} \st\ $\forces{\poP}{\utpoQ\in\calP}$, we have
$\poP\ast\utpoQ\in\calP$.

For an iterable class $\mathcal{P}$ of posets, a cardinal $\mu$ is called {\it Laver-generically
supercompact for $\mathcal{P}$}, if, for any $\mathbb{P}\in\mathcal{P}$ and $\lambda\in\On$,
there is a $\poP$-name $\utpoQ$\vspace{-0.5\smallskipamount} with $\forces{\poP}{\utpoQ\in\calP}$ \st, letting
$\poQ=\poP\ast\utpoQ$,
there are $j$, $M\subseteq\uniV[\genH]$ for $(\uniV, \mathbb{Q})$-generic
$\genH$ such that

1) $\elembed{j}{V}{M}$,\smallskip

2) $crit(j)=\mu$, $j(\mu)>\lambda$,\smallskip

3) $\cardof{\poQ}\leq j(\mu)$,\smallskip

4) $\poP$, $\genH\in M$ and \smallskip

5) $j\imageof\lambda\in M$.\\\\
The notion of Laver-generically superhugeness is obtained when \assert{5} is replaced by

5') $j\imageof j(\mu)\in M$.

The notion of Laver-generically large cardinal for $\calP$ given here is stronger than the one
introduced in \cite{II} and is called there the {\it strongly} and {\it tightly}
Laver-generically large cardinal (the strongness corresponds the usage of two-step
iteration in the definition instead of just $\poP\circleq\poQ$, and the tightness the
condition \assert{3}).

In my talk, I will give a proof of the following:\quad
For many natural iterable class of proper posets $\mathcal{P}$, a
Laver-generically supercompact cardinal $\mu$ for $\poP$ is either $\aleph_2$ or very large (if it
exists),
and the continuum is either $\aleph_1$ or $\aleph_2$, or $\geq\mu$ in case of very large
$\mu$, where it depends on $P$ which scenario we have.

If time allows, I will also sketch a proof of the following theorem:\quad
If $\mathcal{P}$ is the class of c.c.c.\ posets (or some other iterable class $\calP$ of posets preserving all
cardinalities but adding some real), and if $\mu$ is Laver-generically superhuge for $\mathcal{P}$, then
$\mu=2^{\aleph_0}$.

At the moment, it is open if the same theorem holds for a Laver-generically supercompact
Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk on Thursday, March 25

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, March 25 "Splitting Localization and prediction numbers" Iván Ongay-Valverde (York University, Canada) In 1993, Newelski and Roslanowski studied some cardinal characteristics related to the unsymmetric game (I, as Geschke, called them the localization numbers). While doing this, they found the n-localization property. When a forcing has this property, you can ensure that all new reals are 'tame' somehow (for example, you do not add Cohen or Random reals). In a different line of study, Andreas Blass worked with some cardinal characteristics related to the idea of guessing correctly a real number given certain amount of information (he called them evasion and prediction numbers). In 2010, it was an open question whether some possible variations of these numbers were known cardinal characteristics or not. Impressively, these two notions are related. In this talk, we will show that the k global adaptive prediction numbers are not any other cardinal characteristic. In particular, they are not the localization numbers. To do this, we will use techniques analogue to Newelski and Roslanowski and we will show that the n-localization can be weakened to get their result. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at! * * * Please note: There will be no talks in the KGRC research seminar on April 1 and April 8 due to the Easter break in Austria.

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 15, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 15, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Speaker: Eric Bayruns Garcia (Cal State San Bernardino)
Title: Belief Content and Rationality: Why Racist Beliefs Are Not Rational

Abstract: I present a novel defense of the evidentialist thesis in the debate between epistemologists who defend this thesis and those who defend the moral encroachment thesis. Both sides of the moral encroachment-evidentialism debate suppose that the belief class of what I call seemingly-rational-racist beliefs obtains. I reject that this belief class of seemingly- rational-racist beliefs obtains on the basis that beliefs with this kind of content are false and evidentially unsupported. I submit that they are false and evidentially unsupported because of how the content of these beliefs relate to the social-linguistic practices and habits that compose racial injustice in the US and other similarly colonized societies. I diagnose that a problem with this debate is that both sides in this debate conceive of the content of race terms and beliefs that attribute negative features to Black, Indigenous and Latinx persons without considering how they function in a racially unjust society.



- - - - Tuesday, Mar 16, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Mateusz Łełyk, University of Warsaw
TBA


- - - - Wednesday, Mar 17, 2021 - - - -

The New York City Category Theory Seminar
For meeting zoom details email N. Yanofsky.

Speaker:     Tobias Fritz, University of Innsbruck.

Date and Time:     Wednesday March 17, 2021, 7:00 - 8:30 PM., on Zoom.

Title:    Categorical Probability and the de Finetti Theorem.


Abstract: I will give an introduction to categorical probability in terms of Markov categories, followed by a discussion of the classical de Finetti theorem within that framework. Depending on whether current ideas work out or not, I may (or may not) also present a sketch of a purely categorical proof of the de Finetti theorem based on the law of large numbers. Joint work with Tomáš Gonda, Paolo Perrone and Eigil Fjeldgren Rischel.



- - - - Thursday, Mar 18, 2021 - - - -



- - - - Friday, Mar 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Paul Blain Levy, University of Birmingham
Broad Infinity and Generation Principles

Broad Infinity is a new and arguably intuitive axiom scheme in set theory. It states that 'broad numbers', which are three-dimensional trees whose growth is controlled, form a set. If the Axiom of Choice is assumed, then Broad Infinity is equivalent to the Ord-is-Mahlo scheme: every closed unbounded class of ordinals contains a regular ordinal.

Whereas the axiom of Infinity leads to generation principles for sets and families and ordinals, Broad Infinity leads to more advanced versions of these principles. The talk explains these principles and how they are related under various prior assumptions: the Axiom of Choice, the Law of Excluded Middle, and weaker assumptions.



Next Week in Logic at CUNY:

- - - - Monday, Mar 22, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 1, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Martin Pleitz (Münster).
Title: Dualism about Generality

Abstract: In my talk I will motivate, outline, and apply a variant of first order predicate logic that can distinguish between two kinds of generality, which I call objectual generality and conceptual generality. To see the difference, compare the two general statements ‘Every human is a featherless biped’ and ‘Every human is a rational animal’. On a charitable understanding, the first sentence is about all humans past and present, as a subcollection of all particular objects currently accessible to us, while the second sentence is not about any particular object at all, but about the interaction of the concepts of being human and being a rational animal. Historically, the quantified sentences of predicate logic have been understood in either of the two ways. Frege understood them as expressing conceptual generalities; hence it was natural for him to call his predicate logic a “Concept Script”. Today, they are usually understood as objectual generalities, manifest both in the idea that a quantified sentence is like a conjunction (or disjunction) of its instances and in the current model theoretic orientation in semantics. But as we can find ourselves in a situation where we want to talk about both kinds of generality (and their interaction), it is worthwhile to develop the resources to express them within a single system. I will outline such a system that results from adding a second pair of quantifiers to regular first order predicate logic, and sketch applications to the notion of analyticity, natural kind predicates, and an ontological argument.



- - - - Tuesday, Mar 23, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mateusz Łełyk, University of Warsaw
Nonequivalent axiomatizations of PA and the Tarski Boundary: Part III

This is a continuation of the talk from Feb 16th. This time we shall study different theories of the form CT[δ]CT−[δ] which are conservative extensions of a PAPA. In particular, we prove the following theorem.

Theorem 2 There exists a family {δf}fω{δf}f∈ω∗ such that for all f,gωf,g∈ω∗
1) CT[δf]CT−[δf] is conservative over PAPA;
2) if fgf⊊g, then CT[δg]CT−[δg] properly extends CT[δf]CT−[δf];
3) if fgf⊥g then CT[δg]CT[δf]CT−[δg]∪CT−[δf] is nonconservative over PAPA (but consistent).

We will finish the proof of the theorem announced in the abstract of part II.



- - - - Wednesday, Mar 24, 2021 - - - -



- - - - Thursday, Mar 25, 2021 - - - -

Philog Seminar
6:30 PM, Thursday, March 25
Rohit Parikh (CUNY) on
The Logic of  Knowledge Based Obligation (joint work with Eric Pacuit (UMD) and Eva Cogan (Brooklyn))

Our obligations depend on what we know.  If we do not know that we need to do X then there is no obligation to actually do X.    However, sometimes there is also an obligation to know and hence also an obligation to inform.  We look into the temporal logic of such issues, relying on work by John Horty and by Parikh and Ramanujam.

A zoom link will be posted on https://philog.arthurpaulpedersen.org/



- - - - Friday, Mar 26, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 26, 11am
The seminar will take place virtually at 11am US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Carolin Antos, University of Konstanz

The 'algebraic' vs. 'non-algebraic' distinction: New impulses for the universe/multiverse debate?

The distinction between 'algebraic' and 'non-algebraic fields in mathematics, coined by Shapiro (1997), plays an important role in discussions about the status of set theory and connects back to the so-called universe/multiverse debate in the philosophy of set theory. In this talk we will see, that this distinction is not as clear cut as is usually assume when using it in the debate. In particular, we will see that in more recent formulations of this distinction, multiversism seems to split into a a strong and a weaker form. This can be translated to a meta-level, when considering the background theory in which set-theoretic multiversism can take place. This offers a more fine-grained picture of multiversism and allows us to mitigate a standard universist objection based on the conception of a multiversist background theory.




Next Week in Logic at CUNY:

- - - - Monday, Mar 29, 2021 - - - -



- - - - Tuesday, Mar 30, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 30, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Paola d’Aquino, Università della Campania -“L. Vanvitelli”
TBA

- - - - Wednesday, Mar 31, 2021 - - - -



- - - - Thursday, Apr 1, 2021 - - - -



- - - - Friday, Apr 2, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 2, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Monroe Eskew University of Vienna
TBA



- - - - Other Logic News - - - -

Conference announcement: Boise Extravaganza in Set Theory (BEST) June 17-20
 
The 2021 Boise Extravaganza in Set Theory will take place in Zoomland during June 17-20. We would be delighted if you will attend! (Please follow https://www.boisestate.edu/math/best for future updates.)

We are currently welcoming applications to speak at BEST from researchers in set theory and related fields. We hope to receive your application by May 1, but we will continue accepting applications as long as there is space. To apply please send your name, institution, career status (and if student, advisor name), talk title, and abstract to best@boisestate.edu.



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

UPDATE: This Week in Logic at CUNY

This Week in Logic at CUNY
I removed the previous week's events from the calendar this time - sorry for any confusion.
Best,
Jonas


This Week in Logic at CUNY:

- - - - Monday, Mar 22, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 1, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Martin Pleitz (Münster).
Title: Dualism about Generality

Abstract: In my talk I will motivate, outline, and apply a variant of first order predicate logic that can distinguish between two kinds of generality, which I call objectual generality and conceptual generality. To see the difference, compare the two general statements ‘Every human is a featherless biped’ and ‘Every human is a rational animal’. On a charitable understanding, the first sentence is about all humans past and present, as a subcollection of all particular objects currently accessible to us, while the second sentence is not about any particular object at all, but about the interaction of the concepts of being human and being a rational animal. Historically, the quantified sentences of predicate logic have been understood in either of the two ways. Frege understood them as expressing conceptual generalities; hence it was natural for him to call his predicate logic a “Concept Script”. Today, they are usually understood as objectual generalities, manifest both in the idea that a quantified sentence is like a conjunction (or disjunction) of its instances and in the current model theoretic orientation in semantics. But as we can find ourselves in a situation where we want to talk about both kinds of generality (and their interaction), it is worthwhile to develop the resources to express them within a single system. I will outline such a system that results from adding a second pair of quantifiers to regular first order predicate logic, and sketch applications to the notion of analyticity, natural kind predicates, and an ontological argument.



- - - - Tuesday, Mar 23, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mateusz Łełyk, University of Warsaw
Nonequivalent axiomatizations of PA and the Tarski Boundary: Part III

This is a continuation of the talk from Feb 16th. This time we shall study different theories of the form CT[δ]CT−[δ] which are conservative extensions of a PAPA. In particular, we prove the following theorem.

Theorem 2 There exists a family {δf}fω{δf}f∈ω∗ such that for all f,gωf,g∈ω∗
1) CT[δf]CT−[δf] is conservative over PAPA;
2) if fgf⊊g, then CT[δg]CT−[δg] properly extends CT[δf]CT−[δf];
3) if fgf⊥g then CT[δg]CT[δf]CT−[δg]∪CT−[δf] is nonconservative over PAPA (but consistent).

We will finish the proof of the theorem announced in the abstract of part II.



- - - - Wednesday, Mar 24, 2021 - - - -



- - - - Thursday, Mar 25, 2021 - - - -

Philog Seminar
6:30 PM, Thursday, March 25
Rohit Parikh (CUNY) on
The Logic of  Knowledge Based Obligation (joint work with Eric Pacuit (UMD) and Eva Cogan (Brooklyn))

Our obligations depend on what we know.  If we do not know that we need to do X then there is no obligation to actually do X.    However, sometimes there is also an obligation to know and hence also an obligation to inform.  We look into the temporal logic of such issues, relying on work by John Horty and by Parikh and Ramanujam.

A zoom link will be posted on https://philog.arthurpaulpedersen.org/



- - - - Friday, Mar 26, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 26, 11am
The seminar will take place virtually at 11am US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Carolin Antos, University of Konstanz

The 'algebraic' vs. 'non-algebraic' distinction: New impulses for the universe/multiverse debate?

The distinction between 'algebraic' and 'non-algebraic fields in mathematics, coined by Shapiro (1997), plays an important role in discussions about the status of set theory and connects back to the so-called universe/multiverse debate in the philosophy of set theory. In this talk we will see, that this distinction is not as clear cut as is usually assume when using it in the debate. In particular, we will see that in more recent formulations of this distinction, multiversism seems to split into a a strong and a weaker form. This can be translated to a meta-level, when considering the background theory in which set-theoretic multiversism can take place. This offers a more fine-grained picture of multiversism and allows us to mitigate a standard universist objection based on the conception of a multiversist background theory.




Next Week in Logic at CUNY:

- - - - Monday, Mar 29, 2021 - - - -



- - - - Tuesday, Mar 30, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 30, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Paola d’Aquino, Università della Campania -“L. Vanvitelli”
TBA

- - - - Wednesday, Mar 31, 2021 - - - -



- - - - Thursday, Apr 1, 2021 - - - -



- - - - Friday, Apr 2, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Apr 2, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Monroe Eskew University of Vienna
TBA



- - - - Other Logic News - - - -

Conference announcement: Boise Extravaganza in Set Theory (BEST) June 17-20
 
The 2021 Boise Extravaganza in Set Theory will take place in Zoomland during June 17-20. We would be delighted if you will attend! (Please follow https://www.boisestate.edu/math/best for future updates.)

We are currently welcoming applications to speak at BEST from researchers in set theory and related fields. We hope to receive your application by May 1, but we will continue accepting applications as long as there is space. To apply please send your name, institution, career status (and if student, advisor name), talk title, and abstract to best@boisestate.edu.



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Peter Koellner (Harvard University)
TITLE: Minimal models and $\beta$-categoricity
DATE: 24 March 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.







Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609























Unusual time for Friday 26th talk by Sakae Fuchino (10:30 am)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time and please notice the UNUSUAL TIME.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Sakaé Fuchino
Date and Time: Friday, March 26th, 2021 - 10:30am to 12:00pm
Title: Laver-generically large cardinal and the Continuum Problem
Abstract:
Let us call a class $\calP$ of posets iterable, if, for any $\poP\in\calP$ and $\calP$-name
$\utpoQ$\vspace{-0.5\smallskipamount} \st\ $\forces{\poP}{\utpoQ\in\calP}$, we have
$\poP\ast\utpoQ\in\calP$.

For an iterable class $\mathcal{P}$ of posets, a cardinal $\mu$ is called {\it Laver-generically
supercompact for $\mathcal{P}$}, if, for any $\mathbb{P}\in\mathcal{P}$ and $\lambda\in\On$,
there is a $\poP$-name $\utpoQ$\vspace{-0.5\smallskipamount} with $\forces{\poP}{\utpoQ\in\calP}$ \st, letting
$\poQ=\poP\ast\utpoQ$,
there are $j$, $M\subseteq\uniV[\genH]$ for $(\uniV, \mathbb{Q})$-generic
$\genH$ such that

1) $\elembed{j}{V}{M}$,\smallskip

2) $crit(j)=\mu$, $j(\mu)>\lambda$,\smallskip

3) $\cardof{\poQ}\leq j(\mu)$,\smallskip

4) $\poP$, $\genH\in M$ and \smallskip

5) $j\imageof\lambda\in M$.\\\\
The notion of Laver-generically superhugeness is obtained when \assert{5} is replaced by

5') $j\imageof j(\mu)\in M$.

The notion of Laver-generically large cardinal for $\calP$ given here is stronger than the one
introduced in \cite{II} and is called there the {\it strongly} and {\it tightly}
Laver-generically large cardinal (the strongness corresponds the usage of two-step
iteration in the definition instead of just $\poP\circleq\poQ$, and the tightness the
condition \assert{3}).

In my talk, I will give a proof of the following:\quad
For many natural iterable class of proper posets $\mathcal{P}$, a
Laver-generically supercompact cardinal $\mu$ for $\poP$ is either $\aleph_2$ or very large (if it
exists),
and the continuum is either $\aleph_1$ or $\aleph_2$, or $\geq\mu$ in case of very large
$\mu$, where it depends on $P$ which scenario we have.

If time allows, I will also sketch a proof of the following theorem:\quad
If $\mathcal{P}$ is the class of c.c.c.\ posets (or some other iterable class $\calP$ of posets preserving all
cardinalities but adding some real), and if $\mu$ is Laver-generically superhuge for $\mathcal{P}$, then
$\mu=2^{\aleph_0}$.

At the moment, it is open if the same theorem holds for a Laver-generically supercompact

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk tomorrow by Anush Tserunyan (1 30 pm in new daylight saving time)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Anush Tserunyan
Date and Time: Friday, March 19th, 2021 - 1:30pm to 3:00pm
Title: Ergodic theorems along trees
Abstract:
In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in the forward orbit of the point $x$. In joint work with Jenna Zomback, we prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields (forward) ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. For free group actions, this strengthens the best known result in this vein due to Bufetov (2000).

Ivan Ongay Valverde
ongay@yorku.ca
York University Postdoc (he/his)

Libre de virus. www.avast.com

Two CMU seminars on Tuesday, March 23

Carnegie Mellon Logic Seminar
TUESDAY, March 23, 2021 Mathematical logic seminar:  3:30 P.M., Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ordinal definability and the structure of large cardinals,  part 1 ABSTRACT: Roughly speaking, Woodin's HOD conjecture asserts that assuming the existence of very large cardinals, arbitrary sets can be closely approximated by definable ones. This talk outlines an approach to the conjecture based on an analysis of the uniqueness properties of ultrafilters and elementary embeddings, which has a number of applications: for example, a proof of a variant of the HOD conjecture for sets definable from ultrafilters, a proof of Woodin's HOD dichotomy theorem from a single strongly compact cardinal, and a proof that past an extendible cardinal, elementary embeddings of the universe of sets are uniquely determined by their codomains. TUESDAY, March 23, 2021 Set Theory Reading Group:  4:30 P.M., Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ordinal definability and the structure of large cardinals, part 2 ABSTRACT: Roughly speaking, Woodin's HOD conjecture asserts that assuming the existence of very large cardinals, arbitrary sets can be closely approximated by definable ones. This talk outlines an approach to the conjecture based on an analysis of the uniqueness properties of ultrafilters and elementary embeddings, which has a number of applications: for example, a proof of a variant of the HOD conjecture for sets definable from ultrafilters, a proof of Woodin's HOD dichotomy theorem from a single strongly compact cardinal, and a proof that past an extendible cardinal, elementary embeddings of the universe of sets are uniquely determined by their codomains.

Reminder of talk today at 10:00 hrs

NUS Logic Seminar
Hello, this is a reminder for Liling Ko's talk today at 10:00 hrs using the usual logic seminar login. It is the same as for next talk which I send in the subsequent email. Best regards, Frank

Logic Seminar 24 March 2021 17:00 hrs at NUS by Philipp Schlicht

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 24 Marc 2020, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Philipp Schlicht Title: Sets and graphs in generalised descriptive set theory URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: While descriptive set theory studies definable sets of words of length omega, generalised descriptive set theory studies words of uncountable regular length. The talk will begin with an introduction to this field and its applications. I will then talk about how one can characterise when a definable set is small or admits a colouring with few colours with respect to an open graph. This is joint work with Dorottya Sziraki.

(KGRC) research seminar talk on Thursday, March 18

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, March 18 "Partition forcing" Jaroslav Šupina (Pavol Jozef Šafárik University in Košice, Slovakia) A. Miller introduced in 1980 a forcing notion we refer to as a partition forcing. Although it is a variant of Sacks' perfect set forcing, it is closely related to Miller's rational perfect set forcing. The talk is devoted to our application of partition forcing in a proof of consistency of $\mathfrak{u}=\mathfrak{i}<\mathfrak{a}_T$. Here, $\mathfrak{i}$ is the minimal cardinality of a maximal independent family, $\mathfrak{u}$ a minimal size of an ultrafilter base, and $\mathfrak{a}_T$ is the minimal cardinality of a maximal family of pairwise almost disjoint subtrees of $2^{<\omega}$. This is a joint work with Vera Fischer. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:   Wojciech Woloszyn (University of Oxford)
TITLE: Modal graph theory as a foundation of mathematics
DATE: 17 March 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











This Friday talk by Anush Tserunyan (1 30 pm in new daylight saving time)

Toronto Set Theory Seminar
Hello everyone,

Today we had a time change in Toronto. Please check how does it differ from your time zone to avoid missing the seminar.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Anush Tserunyan
Date and Time: Friday, March 19th, 2021 - 1:30pm to 3:00pm
Title: Ergodic theorems along trees
Abstract:
In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in the forward orbit of the point $x$. In joint work with Jenna Zomback, we prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields (forward) ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. For free group actions, this strengthens the best known result in this vein due to Bufetov (2000).

Ivan Ongay Valverde
ongay@yorku.ca
York University Postdoc (he/his)

Libre de virus. www.avast.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 15, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 15, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Speaker: Eric Bayruns Garcia (Cal State San Bernardino)
Title: Belief Content and Rationality: Why Racist Beliefs Are Not Rational

Abstract: I present a novel defense of the evidentialist thesis in the debate between epistemologists who defend this thesis and those who defend the moral encroachment thesis. Both sides of the moral encroachment-evidentialism debate suppose that the belief class of what I call seemingly-rational-racist beliefs obtains. I reject that this belief class of seemingly- rational-racist beliefs obtains on the basis that beliefs with this kind of content are false and evidentially unsupported. I submit that they are false and evidentially unsupported because of how the content of these beliefs relate to the social-linguistic practices and habits that compose racial injustice in the US and other similarly colonized societies. I diagnose that a problem with this debate is that both sides in this debate conceive of the content of race terms and beliefs that attribute negative features to Black, Indigenous and Latinx persons without considering how they function in a racially unjust society.



- - - - Tuesday, Mar 16, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Mateusz Łełyk, University of Warsaw
TBA


- - - - Wednesday, Mar 17, 2021 - - - -

The New York City Category Theory Seminar
For meeting zoom details email N. Yanofsky.

Speaker:     Tobias Fritz, University of Innsbruck.

Date and Time:     Wednesday March 17, 2021, 7:00 - 8:30 PM., on Zoom.

Title:    Categorical Probability and the de Finetti Theorem.


Abstract: I will give an introduction to categorical probability in terms of Markov categories, followed by a discussion of the classical de Finetti theorem within that framework. Depending on whether current ideas work out or not, I may (or may not) also present a sketch of a purely categorical proof of the de Finetti theorem based on the law of large numbers. Joint work with Tomáš Gonda, Paolo Perrone and Eigil Fjeldgren Rischel.



- - - - Thursday, Mar 18, 2021 - - - -



- - - - Friday, Mar 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Paul Blain Levy, University of Birmingham
Broad Infinity and Generation Principles

Broad Infinity is a new and arguably intuitive axiom scheme in set theory. It states that 'broad numbers', which are three-dimensional trees whose growth is controlled, form a set. If the Axiom of Choice is assumed, then Broad Infinity is equivalent to the Ord-is-Mahlo scheme: every closed unbounded class of ordinals contains a regular ordinal.

Whereas the axiom of Infinity leads to generation principles for sets and families and ordinals, Broad Infinity leads to more advanced versions of these principles. The talk explains these principles and how they are related under various prior assumptions: the Axiom of Choice, the Law of Excluded Middle, and weaker assumptions.



Next Week in Logic at CUNY:

- - - - Monday, Mar 22, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 1, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu

Martin Pleitz (Münster).
Title: Dualism about Generality

Abstract: In my talk I will motivate, outline, and apply a variant of first order predicate logic that can distinguish between two kinds of generality, which I call objectual generality and conceptual generality. To see the difference, compare the two general statements ‘Every human is a featherless biped’ and ‘Every human is a rational animal’. On a charitable understanding, the first sentence is about all humans past and present, as a subcollection of all particular objects currently accessible to us, while the second sentence is not about any particular object at all, but about the interaction of the concepts of being human and being a rational animal. Historically, the quantified sentences of predicate logic have been understood in either of the two ways. Frege understood them as expressing conceptual generalities; hence it was natural for him to call his predicate logic a “Concept Script”. Today, they are usually understood as objectual generalities, manifest both in the idea that a quantified sentence is like a conjunction (or disjunction) of its instances and in the current model theoretic orientation in semantics. But as we can find ourselves in a situation where we want to talk about both kinds of generality (and their interaction), it is worthwhile to develop the resources to express them within a single system. I will outline such a system that results from adding a second pair of quantifiers to regular first order predicate logic, and sketch applications to the notion of analyticity, natural kind predicates, and an ontological argument.



- - - - Tuesday, Mar 23, 2021 - - - -



- - - - Wednesday, Mar 24, 2021 - - - -



- - - - Thursday, Mar 25, 2021 - - - -



- - - - Friday, Mar 26, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 26, 11am
The seminar will take place virtually at 11am US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Carolin Antos, University of Konstanz


- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

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If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Talk tomorrow by Anush Tserunyan (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please remember that Toronto just had a daylight saving change of time.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Anush Tserunyan
Date and Time: Friday, March 19th, 2021 - 1:30pm to 3:00pm
Title: Ergodic theorems along trees
Abstract:
In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in the forward orbit of the point $x$. In joint work with Jenna Zomback, we prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields (forward) ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. For free group actions, this strengthens the best known result in this vein due to Bufetov (2000).

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk by Anush Tserunyan Friday 19th (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Menachem Kojman
Date and Time: Friday, March 19th, 2021 - 1:30pm to 3:00pm
Title: Ergodic theorems along trees
Abstract:
In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in the forward orbit of the point $x$. In joint work with Jenna Zomback, we prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields (forward) ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. For free group actions, this strengthens the best known result in this vein due to Bufetov (2000).

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

CMU seminars on Tuesday, March 16

Carnegie Mellon Logic Seminar
TUESDAY, March 16, 2021 Mathematical logic seminar:  3:30 P.M., Online, Clinton Conley, CMU Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Dividing the sphere by rotations, part 1 ABSTRACT: We say that a subset A of the sphere r-divides it if r-many rotations of A perfectly tile the sphere's surface.  Such divisions were first exhibited by Robinson ('47) and developed by Mycielski ('55).  We discuss a colorful approach to finding these divisions which are Lebesgue measurable or possess the property of Baire.  This includes joint work with J. Grebik, A. Marks, O. Pikhurko, and S. Unger. TUESDAY, March 16, 2021 Set Theory Reading Group:  4:30 P.M., Online, Clinton Conley, CMU Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Dividing the sphere by rotations, part 2 ABSTRACT: We say that a subset A of the sphere r-divides it if r-many rotations of A perfectly tile the sphere's surface.  Such divisions were first exhibited by Robinson ('47) and developed by Mycielski ('55).  We discuss a colorful approach to finding these divisions which are Lebesgue measurable or possess the property of Baire.  This includes joint work with J. Grebik, A. Marks, O. Pikhurko, and S. Unger.

Tomorrow talk by Menachem Kojman (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Menachem Kojman
Date and Time: Friday, March 12th, 2021 - 1:30pm to 3:00pm
Title:  Strong colorings over partitions
Abstract:
Strong colorings over partitions were introduced last year by Chen-Mertens, Kojman and Steprans.

In the talk I will present the subject and continue to present the next step of the theory, which was developed in a recent  joint work by Kojman, Rinot and Steprans.

The advances include stretching arguments which use Walks on Ordinals. I will present this new technique.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Boise Extravaganza in Set Theory June 17-20

Conference
The 2021 Boise Extravaganza in Set Theory will take place in Zoomland during June 17-20. We would be delighted if you will attend! (Please follow https://www.boisestate.edu/math/best for future updates.) We are currently welcoming applications to speak at BEST from researchers in set theory and related fields. We hope to receive your application by May 1, but we will continue accepting applications as long as there is space. To apply please send your name, institution, career status (and if student, advisor name), talk title, and abstract to best@boisestate.edu. The BEST conference particularly aims to support the careers of young researchers, so please pass this announcement along to students and colleagues who may not have received it. We strongly encourage persons from groups underrepresented in mathematics to apply. Plenary speakers: David Fernández-Bretón (UNAM) Victoria Gitman (CUNY Graduate Center) Jun Le Goh (University of Wisconsin) Lynne Yengulalp (Wake Forest University) Joseph Zielinski (North Texas) Additional confirmed speakers Filippo Calderoni (University of Illinois, Chicago) Thomas Gilton (University of Pittsburgh) Osvaldo Guzmán González (UNAM) Randall Holmes (Boise State University) Aristotelis Panagiotopoulos (Munster) Nick Ramsey (UCLA) Kameryn Williams (Hawaii) Jenna Zomback (UIUC) … and more to come! BEST is an international conference featuring talks on a broad range of recent advances in set theory and related fields of research. The conference is organized by the Set Theory group at Boise State University. Under normal circumstances BEST is supported by NSF, AAAS–Pacific Division, and Boise State University. Organizers: Liljana Babinkostova, John Clemens, Samuel Coskey, Marion Scheepers Scientific support: Natasha Dobrinen, Simon Thomas
Link to more info

Logic Seminar 18 March 2021 10:00 hrs at NUS by Ko Liling (Notre Dame)

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Thursday, 18 March 2021, 10:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Ko Liling Title: Towards finding a lattice of fickleness strictly above omega^2 URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Given a finite lattice L that can be embedded in the recursively enumerable (r.e.) Turing degrees (R,<) we do not in general know how to characterize the degrees d in R below which L can be bounded. The important characterizations known so far are of the L_7 and 1-3-1 lattices, where the former is bounded exactly by the degrees with fickleness strictly above omega and the latter is bounded exactly by the degrees containing sets of fickleness greater equal omega^omega. Given that the fickleness hierarchy collapses exactly to the powers of omega with the first few levels being 0,omega,omega^2,...,omega^omega, we want to find a lattice that characterizes the levels strictly above omega^2. We begin by exhausting the lattices L that are as ``small'' as L_7 and 1-3-1, but these lattices turn out to characterize the levels strictly above omega or from omega^omega onwards, if L is not already embeddable below all non-zero r.e. degrees. We even considered small infinite lattices but they too behave like L_7 or 1-3-1. We discovered three lattices besides 1-3-1 that also characterize the levels from omega^omega onwards. Our search for a candidate characterising the levels strictly above omega^2 therefore involves the lattice-theoretic problem of finding lattices that do not contain any of the four sublattices which characterise the levels from omega^omega onwards as a sublattice. Using this criterion as a heuristic we introduce the wide diamond lattice as a candidate, though we conjecture that this lattice also behaves like 1-3-1.

Peter Koellner: Minimal Models and β-Categoricity

Bristol Logic and Set Theory Seminar
Peter Koellner (Harvard) Minimal Models and β-Categoricity Bristol Logic and Set Theory Seminar 10th March 2021, 4:00 pm – 5:30 pm Zoom, On-line Please email Sam Adam-Day for the link: me@samadamday.com ----------------------- Abstract: Let us say that a theory $T$ in the language of set theory is \textit{$\beta$-consistent at $\alpha$} if there is a transitive model of $T$ of height $\alpha$, and let us say that it is \textit{$\beta$-categorical at $\alpha$} iff there is at most one transitive model of $T$ of height $\alpha$. Let us also assume, for ease of formulation, that there are arbitrarily large $\alpha$ such that $\ZFC$ is $\beta$-consistent at $\alpha$. The sentence $\VEL$ has the feature that $\ZFC+\VEL$ is $\beta$-categorical at $\alpha$, for every $\alpha$. If we assume in addition that $\ZFC+\VEL$ is $\beta$-consistent at $\alpha$, then the uniquely determined model is $L_\alpha$, and the minimal such model, $L_{\alpha_0}$, is model of determined by the $\beta$-categorical theory $\ZFC+\VEL+M$, where $M$ is the statement ``There does not exist a transitive model of $\ZFC$.'' It is natural to ask whether $\VEL$ is the only sentence that can be $\beta$-categorical at $\alpha$; that is, whether, there can be a sentence $\phi$ such that $\ZFC+\phi$ is $\beta$-categorical at $\alpha$, $\beta$-consistent at $\alpha$, and where the unique model is not $L_\alpha$. In the early 1970s Harvey Friedman proved a partial result in this direction. For a given ordinal $\alpha$, let $n(\alpha)$ be the next admissible ordinal above $\alpha$, and, for the purposes of this discussion, let us say that an ordinal $\alpha$ is \textit{minimal} iff a bounded subset of $\alpha$ appears in $L_{n(\alpha)}\setminus L_\alpha$. [Note that $\alpha_0$ is minimal (indeed a new subset of $\omega$ appears as soon as possible, namely, in a $\Sigma_1$-definable manner over $L_{\alpha_0+1}$) and an ordinal $\alpha$ is non-minimal iff $L_{n(\alpha)}$ satisfies that $\alpha$ is a cardinal.] Friedman showed that for all $\alpha$ which are non-minimal, $\VEL$ is the only sentence that is $\beta$-categorical at $\alpha$. The question of whether this is also true for $\alpha$ which are minimal has remained open. In this talk I will describe some joint work with Hugh Woodin that bears on this question. In general, when approaching a ``lightface'' question (such as the one under consideration) it is easier to first address the ``boldface'' analogue of the question by shifting from the context of $L$ to the context of $L[x]$, where $x$ is a real. In this new setting everything is relativized to the real $x$: For an ordinal $\alpha$, we let $n_x(\alpha)$ be the first $x$-admissible ordinal above $\alpha$, and we say that $\alpha$ is $x$-\textit{minimal} iff a bounded subset of $\alpha$ appears in $L_{n_x(\alpha)}[x]\setminus L_{\alpha}[x]$. \begin{theorem*} Assume $M_1^\#$ exists and is fully iterable. There is a sentence $\phi$ in the language of set theory with two additional constants, \r{c} and \r{d}, such that for a Turing cone of $x$, interpreting \r{c} by $x$, for all $\a$ \begin{enumerate} \item[(1)] if $L_\alpha[x]\sat\ZFC$ then there is an interpretation of \r{d} by something in $L_\alpha[x]$ such that there is a $\beta$-model of $\ZFC+\phi$ of height $\alpha$ and not equal to $L_\alpha[x]$, and \item[(2)] if, in addition, $\alpha$ is $x$-minimal, then there is a \textit{unique} $\beta$-model of $\ZFC+\phi$ of height $\alpha$ and not equal to $L_\alpha[x]$. \end{enumerate} \end{theorem*} The sentence $\phi$ asserts the existence of an object which is external to $L_\alpha[x]$ and which, in the case where $\alpha$ is minimal, is canonical. The object is a branch $b$ through a certain tree in $L_\alpha[x]$, and the construction uses techniques from the HOD analysis of models of determinacy. In this talk I will sketch the proof, describe some additional features of the singleton, and say a few words about why the lightface version looks difficult.

(KGRC) research seminar talk on Thursday, March 11

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, March 11 The exact consistency strength of "$AD^+$ + all sets are universally Baire" Sandra Müller (TU Wien and KGRC) The large cardinal strength of the Axiom of Determinacy when enhanced with the hypothesis that all sets of reals are universally Baire is known to be much stronger than the Axiom of Determinacy itself. In fact, Sargsyan conjectured it to be as strong as the existence of a cardinal that is both a limit of Woodin cardinals and a limit of strong cardinals. Larson, Sargsyan and Wilson showed in 2014 that this would be optimal via a generalization of Woodin's derived model construction. We will discuss a new translation procedure for hybrid mice extending work of Steel, Zhu and Sargsyan and use this to prove Sargsyan's conjecture. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Logic Seminar 10 March 2021 17:00 hrs at NUS

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 10 March 2020, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Zekun Jia Title: Two Ramsey-theoretic statements in models where AC fails Abstract: There are a lot of theorems in Ramsey theory whose proof explicitly or implicitly uses the Axiom of Choice. This talk will focus on Ramsey's Theorem and Open Ramsey Theorem in three models of set theory where the Axiom of Choice fails (the basic Cohen model, the basic Fraenkel model, and the ordered Mostowski model), as well as some consistency and independence results that follow. Also, the usual proof of Open Ramsey Theorem on omega given by Galvin and Prikry assumes the Axiom of Dependent Choice, and this talk will sketch an improvement on that proof to make it purely constructive. This project is advised by Zach Norwood. URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html

Talk by Menachem Kojman this Friday 12th (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Menachem Kojman
Date and Time: Friday, March 12th, 2021 - 1:30pm to 3:00pm
Title:  Strong colorings over partitions
Abstract:
Strong colorings over partitions were introduced last year by Chen-Mertens, Kojman and Steprans.

In the talk I will present the subject and continue to present the next step of the theory, which was developed in a recent  joint work by Kojman, Rinot and Steprans.

The advances include stretching arguments which use Walks on Ordinals. I will present this new technique.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:  Carolin Antos (University of Konstanz)
TITLE: The “algebraic” vs. “non-algebraic” distinction: New impulses for the universe/multiverse debate?
DATE: 10 March 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.







Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609






















Upcoming CMU mathematical logic seminars

Carnegie Mellon Logic Seminar
TUESDAY, March 9, 2021 Mathematical logic seminar:  3:30 P.M., Online, Andrew Swan, CMU Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Quotient inductive types without choice ABSTRACT: Inductive types are types that are freely generated by collections of algebraic operators. A common example is the collection of countably branching trees, which is freely generated by two operators: 1) there is a countably branching tree, which we visualise as the trivial tree with one node and no branches, and 2) given a countable sequence of countably branching trees, there is a new countably branching tree, which we visualise as a root together with a branch for each tree in the sequence. Quotient inductive types are freely generated by two processes simultaneously. As well as generating new elements by operators, as for inductive types, we can also identify two elements together according to a collection of equations. This is often illustrated with the example of unordered countably branching trees, where we add equations to the example above identifying two trees if we can obtain one from the other by reordering the branches according to a permutation of the naturals. Inductive types, formalised as W types, are well known to exist in any elementary topos with natural number object, and in particular the category of sets under the assumptions of ZF. However, Blass gave an example of a quotient inductive type that can be constructed in the category of sets assuming the existence of an uncountable regular cardinal, but can't probably be constructed in ZF. In between these cases are classes of quotient inductive types obtained by placing restrictions on the set of equations that can be explicitly constructed in ZF but require more elaborate proofs than for W types. I will talk about two such classes; W types with reductions in presheaves and image preserving QW-types in sets. The former were developed as a tool in the semantics of homotopy type theory, giving in particular a version of the small object argument and a construction of higher inductive types suitable for categories without exact quotients or infinite colimits. The latter generalise a construction of hereditarily countable sets due to Jech and include the famous example of unordered countably branching trees above. THURSDAY, March 11, 2021 Model Theory Seminar:  10:00 A.M., Online, Adi Jarden, Ariel University Center of Samaria Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Uniqueness Triples and the Diamond Principle, Part II ABSTRACT: We work with a pre-𝜆-frame, which is an abstract elementary class (AEC) endowed with a collection of basic types and a non-forking relation satisfying certain natural properties with respect to models of cardinality 𝜆. We investigate the density of uniqueness triples in a given pre-𝜆-frames, that is, under what circumstances every basic triple admits a non-forking extension that is a uniqueness triple. Prior results in this direction required strong hypotheses on s. Our main result is an improvement, in that we assume far fewer hypotheses on s. In particular, we do not require s to satisfy the extension, uniqueness, stability, or symmetry properties, or any form of local character, though we do impose the amalgamation and stability properties in 𝜆+, and we do assume ♢(𝜆+). As a corollary, by applying our main result to the trivial 𝜆-frame, it follows that in any AEC K satisfying modest hypotheses on K𝜆 and K𝜆+, the set of *-domination triples in K𝜆 is dense among the non-algebraic triples. We also apply our main result to the non-splitting relation, obtaining the density of uniqueness triples from very few hypotheses. TUESDAY, March 16, 2021 Mathematical logic seminar:  3:30 P.M., Online, Clinton Conley, CMU Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Dividing the sphere by rotations, part 1 ABSTRACT: We say that a subset A of the sphere r-divides it if r-many rotations of A perfectly tile the sphere's surface.  Such divisions were first exhibited by Robinson ('47) and developed by Mycielski ('55).  We discuss a colorful approach to finding these divisions which are Lebesgue measurable or possess the property of Baire.  This includes joint work with J. Grebik, A. Marks, O. Pikhurko, and S. Unger. TUESDAY, March 16, 2021 Set Theory Reading Group:  4:30 P.M., Online, Clinton Conley, CMU Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Dividing the sphere by rotations, part 2 ABSTRACT: We say that a subset A of the sphere r-divides it if r-many rotations of A perfectly tile the sphere's surface.  Such divisions were first exhibited by Robinson ('47) and developed by Mycielski ('55).  We discuss a colorful approach to finding these divisions which are Lebesgue measurable or possess the property of Baire.  This includes joint work with J. Grebik, A. Marks, O. Pikhurko, and S. Unger. TUESDAY, March 23, 2021 Mathematical logic seminar:  3:30 P.M., Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ordinal definability and the structure of large cardinals, part 1 ABSTRACT: Roughly speaking, Woodin's HOD conjecture asserts that assuming the existence of very large cardinals, arbitrary sets can be closely approximated by definable ones. This talk outlines an approach to the conjecture based on an analysis of the uniqueness properties of ultrafilters and elementary embeddings, which has a number of applications: for example, a proof of a variant of the HOD conjecture for sets definable from ultrafilters, a proof of Woodin's HOD dichotomy theorem from a single strongly compact cardinal, and a proof that past an extendible cardinal, elementary embeddings of the universe of sets are uniquely determined by their codomains. TUESDAY, March 23, 2021 Set Theory Reading Group:  4:30 P.M., Online, Gabriel Goldberg, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ordinal definability and the structure of large cardinals, part 2 ABSTRACT: Roughly speaking, Woodin's HOD conjecture asserts that assuming the existence of very large cardinals, arbitrary sets can be closely approximated by definable ones. This talk outlines an approach to the conjecture based on an analysis of the uniqueness properties of ultrafilters and elementary embeddings, which has a number of applications: for example, a proof of a variant of the HOD conjecture for sets definable from ultrafilters, a proof of Woodin's HOD dichotomy theorem from a single strongly compact cardinal, and a proof that past an extendible cardinal, elementary embeddings of the universe of sets are uniquely determined by their codomains. TUESDAY, March 30, 2021 Mathematical logic seminar:  3:30 P.M., Online, Colin Jahel, Université Claude Bernard Lyon 1 Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Some progress on the unique ergodicity problem ABSTRACT: In 2005, Kechris, Pestov and Todorcevic exhibited a correspondence between combinatorial properties of structures and dynamical properties of their automorphism groups. In 2012, Angel, Kechris and Lyons used this correspondence to show the unique ergodicity of all the actions of some subgroups of $S_\infty$. In this talk, I will give an overview of the aforementioned results and discuss recent work generalizing results of Angel, Kechris and Lyons. TUESDAY, April 20, 2021 Mathematical logic seminar:  3:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA TUESDAY, April 20, 2021 Set Theory Reading Group:  4:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA TUESDAY, April 27, 2021 Mathematical logic seminar:  3:30 P.M., Online, Omer Ben-Neria, The Hebrew University of Jerusalem Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Tree-like scales and free subsets of set theoretic algebras, part 1 TUESDAY, April 27, 2021 Set Theory Reading Group:  4:30 P.M., Online, Omer Ben-Neria, The Hebrew University of Jerusalem Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Tree-like scales and free subsets of set theoretic algebras, part 2

Talk tomorrow by Alan Dow (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Alan Dow
Date and Time: Friday, March 5th, 2021 - 1:30pm to 3:00pm
Title: On the cardinality of separable pseudoradial spaces
Abstract:
A point is in the radial closure of a set A if there is a well-ordered sequence from A converging to the point. A set is radially closed if all points in the radial closure are in the set.  A space is radial if the radial closure of a set equals its closure and is pseudoradial if every radially closed set is closed.

 One can observe that the notions of Frechet-Urysohn and sequential are the related notions when restricted to the usual countable sequences. Motivatedby some work and questions by Santi Spadaro,  Istvan Juhasz asked about  the implicit question raised by the title.  We discuss our progress on the problem in joint work with Istvan Juhasz.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Alexandra Pasi: Forcing $\aleph_1$-Free Groups to Be Free

PALS
Tuesday (March 9) at 1pm MST Zoom Meeting ID: https://cuboulder.zoom.us/j/96896272260 Passcode: PALS2021 Speaker: Alexandra Pasi (Baylor) Title: Forcing $\aleph_1$-Free Groups to Be Free Abstract: $\aleph_1$-free groups, abelian groups whose countable subgroups are free, are objects of both algebraic and set-theoretic interest. Illustrating this, we note that $\aleph_1$-free groups, and in particular the question of when $\aleph_1$-free groups are free, were central to the resolution of the Whitehead problem as undecidable. In elucidating the relationship between $\aleph_1$-freeness and freeness, we prove the following result: an abelian group $G$ is $\aleph_1$-free in a countable transitive model of $\operatorname{ZFC}$ (and thus by absoluteness, in every transitive model of $\operatorname{ZFC}$) if and only if it is free in some generic model extension. We would like to answer the more specific question of when an $\aleph_1$-free group can be forced to be free while preserving the cardinality of the group. For groups of size $\aleph_1$, we establish a necessary and sufficient condition for when such forcings are possible. We also identify a number of existing and novel forcings which force such $\aleph_1$-free groups of size $\aleph_1$ to become free with cardinal preservation. These forcings lay the groundwork for a larger project which uses forcing to explore various algebraic properties of $\aleph_1$-free groups and develops new set-theoretical tools for working with them.
Link to more info

Fwd: Fw: Kobe Set Theory Workshop 2021 -- on the occasion of Sakaé Fuchino's retirement --

Toronto Set Theory Seminar
An interesting workshop
Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com


From: Joerg Brendle <brendle@kobe-u.ac.jp>
Sent: Tuesday, March 2, 2021 4:58 AM
To: brendle <brendle@kobe-u.ac.jp>; SAKAI Hiroshi <hsakai@people.kobe-u.ac.jp>
Subject: Kobe Set Theory Workshop 2021 -- on the occasion of Sakaé Fuchino's retirement --
 
EXTERNAL EMAIL:
dear colleague,

we will have a zoom workshop at Kobe University on the occasion of
Sakaé Fuchino's retirement from March 9 (tue) till March 11 (thu).
(Sakaé retired last year and the originally planned workshop was
cancelled because of COVID. we now decided to have it online.)
see  
for the program etc.

invited speakers are:
 - Sakaé Fuchino
 - David Asperó (University of East Anglia)
 - Joan Bagaria (University of Barcelona)
 - Piotr Borodulin-Nadzieja (University of Wrocław)
 - Andrew Brooke-Taylor (University of Leeds)
 - Joel David Hamkins (Oxford University)
 - Daisuke Ikegami (Shibaura Institute of Technology)
 - Chris Lambie-Hanson (Virginia Commonwealth University) 
 - Paul Larson (Miami University)
 - Diego Mejía (Shizuoka University)
 - Toshimichi Usuba (Waseda University)
 - Teruyuki Yorioka (Shizuoka University)
 
anybody can attend, but a preregistration via zoom at the following page is
necessary:
once you register you should get a link for the zoom meeting within one day.
we'd be grateful if you could distribute this information to colleagues. 
for questions please contact me or Hiroshi at hsakai@people.kobe-u.ac.jp

we very much hope that you can attend online.

best wishes,

jörg brendle



Talk this Friday by Alan Dow (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Alan Dow
Date and Time: Friday, March 5th, 2021 - 1:30pm to 3:00pm
Title: On the cardinality of separable pseudoradial spaces
Abstract:
A point is in the radial closure of a set A if there is a well-ordered sequence from A converging to the point. A set is radially closed if all points in the radial closure are in the set.  A space is radial if the radial closure of a set equals its closure and is pseudoradial if every radially closed set is closed.

 One can observe that the notions of Frechet-Urysohn and sequential are the related notions when restricted to the usual countable sequences. Motivatedby some work and questions by Santi Spadaro,  Istvan Juhasz asked about  the implicit question raised by the title.  We discuss our progress on the problem in joint work with Istvan Juhasz.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Kobe Set Theory Workshop 2021: March 9-11

Conference
Hello everyone. Last year, Sakaé Fuchino retired from Kobe University. On this occasion, we will have the following online workshop. We look forward to your participation! Kobe Set Theory Workshop 2021 — on the occasion of Sakaé Fuchino’s retirement — (Online Workshop via ZOOM) Dates: March 9th (Tue.) — 11th (Thu.) Webpage: http://www2.kobe-u.ac.jp/~hsakai/Fuchino2021/ Speakers: - Sakaé Fuchino (Kobe University) - Joan Bagaria (University of Barcelona) - Joel David Hamkins (Oxford University) - Paul Larson (Miami University) - David Aspero (University of East Anglia) - Piotr Borodulin-Nadzieja (University of Wrocław) - Andrew Brooke-Taylor (University of Leeds) - Chris Lambie-Hanson (Virginia Commonwealth University) - Teruyuki Yorioka (Shizuoka University) - Toshinmichi Usuba (Waseda University) - Daisuke Ikegami (Shibaura Institute of Technology) - Diego Mejia (Shizuoka University) Registration: Only registered participants will have access to the ZOOM Meeting link. For the registration, please click the following link. https://kobe-u-ac-jp.zoom.us/meeting/register/tZYqde2oqjstH9QW5CXr6eWuUM3oMdbQ7xFE After the registration, organizers will approve it within a day. Then, you will receive the ZOOM Meeting link by e-mail. If you have any questions, please contact Hiroshi Sakai by e-mail. Contact: hsakai@people.kobe-u.ac.jp
Link to more info

(KGRC) research seminar talk on Thursday, March 4

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, March 4 "Asymptotic differential algebra and logarithmic transseries" Allen Gehret (KGRC) In this talk I will give a brief introduction to the subject 'Asymptotic Differential Algebra' and an overview of the logarithmic transseries programme. The intuition originates in freshman calculus (specifically: limits, l'hopital's rule, convergence/divergence of integrals and series, asymptotic expansions). The mathematical concepts primarily involve various flavors of fields (equipped with a derivation and/or a valuation and/or an ordering). The logical content will be minimal: first-order languages, model completeness, quantifier elimination. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Mar 1, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 1, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Shay Logan (Kansas State)
Title: The Easy Argument Against Noncontractive Logics Doesn’t Work

Abstract: The Easy Argument against noncontractivism is the argument that essentially amounts to pointing out that contraction is just repeating oneself. The purpose of this talk is to explain why the Easy Argument fails. I show first that the Easy Argument fails by being insufficiently precise, since there are many ways we can combine premises in an argument. After correcting for this, the Easy Argument then fails by being straightforwardly invalid. The premises required to correct for *this* failure, however, have controversial consequences. Altogether, it seems arguments against noncontractive logics, if there are any, will be Hard—not Easy—Arguments.



- - - - Tuesday, Mar 2, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 2, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Ali Enayat, University of Gothenburg
PA with a class of indiscernibles

This talk focuses on the theory PAI (I for Indiscernibles), a theory formulated in the language of PA augmented with a unary predicate I(x). Models of PAI are of the form (M,I) where (1) M is a model of PA, (2) I is a proper class of M, i.e., I is unbounded in M and (M,I) satisfies PA*, and (3) I forms a class of indiscernibles over M. The formalizability of the Infinite Ramsey Theorem in PA makes it clear that PAI is a conservative extension of PA. As we will see, nonstandard models of PA (of any cardinality) that have an expansion to a model of PAI are precisely those nonstandard models PA that can carry an inductive partial satisfaction class. The formulation and investigation of PAI was inspired by my work on the set theoretical sibling ZFI of PAI, whose behavior I will also compare and contrast with that of PAI.



- - - - Wednesday, Mar 3, 2021 - - - -

The New York City Category Theory Seminar
For meeting zoom details email N. Yanofsky.
Date and Time:     Wednesday Mar 3, 2021, 7:00 - 8:30 PM., on Zoom.

Speaker:     Joshua Sussan, Medgar Evers, CUNY.

Title:    Categorification and quantum topology.


Abstract: The Jones polynomial of a link could be defined through the representation theory of quantum sl(2). It leads to a 3-manifold invariant and 2+1 dimensional TQFT. In the mid 1990s, Crane and Frenkel outlined the categorification program with the aim of constructing a 3+1 dimensional TQFT by upgrading the representation theory of quantum sl(2) to some categorical structures. We will review these ideas and give examples of various categorifications of quantum sl(2) constructions.




- - - - Thursday, Mar 4, 2021 - - - -

Philog seminar

Thursday March 4 at 6:30 PM

Jenn McDonald, CUNY Graduate Center

Causal Models as Relative to Modal Profile

Abstract        A recent development in the philosophy of causation uses the framework of causal models, such as structural equation models, to define actual causation. There are two components to such a definition. The first is to identify how to define causation in terms of a given model or given class of models. The second is to provide an account of what qualifies models as given – or apt – such that they can be plugged into the first stage. A naïve hypothesis is that a model is apt just in case it is accurate. In this talk I will argue, however, that the accuracy of a model is not a determinate function of a model, an interpretation, and a situation. A given model on a given interpretation can still be deemed accurate or inaccurate of the same situation. As I demonstrate, this is because accuracy is relative to a set of background possibilities – what I call a modal profile.  I argue that this reveals a heretofore hidden element in how causal models represent – that models represent situations only relative to some modal profile or other. I propose that this calls for an additional component of an interpretation: an interpretation is an assignment of content to the variables and a specification of modal profile.

A zoom link will be posted on https://philog.arthurpaulpedersen.org/


Next speaker:  Nur Dean, Farmingdale College






- - - - Friday, Mar 5, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Hiroshi Sakai, Kobe University
Generalized stationary reflection and cardinal arithmetic

The stationary reflection principle, which is often called the Weak Reflection Principle, is known to have many interesting consequences. As for cardinal arithmetic, it implies that λω=λλω=λ for all regular cardinal λω2λ≥ω2. In this talk, we will discuss higher analogues of this stationary reflection principle and their consequences on cardinal arithmetic.




Next Week in Logic at CUNY:

- - - - Monday, Mar 8, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 8, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Hitoshi Omori (Bochum)
Title: Two applications of Herzberger’s semantics

Abstract: In his paper “Dimensions of truth”, Hans Herzberger develops a semantic framework that captures both classical logic and weak Kleene logic through one and the same interpretation. The aim of this talk is to apply the simple idea of Herzberger to two kinds of many-valued semantics. This application will be led by the following two questions.

(i) Is de Finetti conditional a conditional?
(ii) What do CL, K3 and LP disagree about?

Note: This is a joint work with Jonas R. B. Arenhart (Santa Catarina).




- - - - Tuesday, Mar 9, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Damir Dzhafarov, University of Connecticut



- - - - Wednesday, Mar 10, 2021 - - - -




- - - - Thursday, Mar 11, 2021 - - - -



- - - - Friday, Mar 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 12, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Hossein Lamei Ramandi, Cornell University
Galvin's question on non-σσ-well ordered linear orders

Assume CC is the class of all linear orders LL such that LL is not a countable union of well ordered sets, and every uncountable subset of LL contains a copy of ω1ω1. We show it is consistent that CC has minimal elements. This answers an old question due to Galvin.



- - - - Other Logic News - - - -



- - - - Web Site - - - -

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(site designed, built & maintained by Victoria Gitman)"

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Talk by Justin Moore tomorrow (1 30pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Justin Moore
Date and Time: Friday, February 26, 2021 - 1:30pm to 3:00pm
Title: On the additivity of strong homology for locally compact separable metric spaces
Abstract:
We show that it is consistent relative to a weakly compact cardinal that strong homology is additive and compactly supported within the class of locally compact separable metric spaces. This complements work of Mardešić and Prasolov showing that the Continuum Hypothesis implies that a countable sum of Hawaiian earrings witnesses the failure of strong homology to possess either of these properties. Our results build directly on work of Lambie-Hanson and the second author which establishes the consistency, relative to a weakly compact cardinal, of $\lim^{s}A=0$  for all $s\geq 1$ for a certain pro-abelian group $A$; we show that that work's arguments carry implications for the vanishing and additivity of the $\lim^{s}$ functors over a substantially more general class of pro-abelian groups indexed by $\mathbb{N}^{\mathbb{N}}$.

This is joint work with Nathaniel Bannister and Jeffrey Bergfalk.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Logic Seminar Wed 3 March 2021 17:00 hrs at NUS

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 3 March 2021, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Desmond Lau Title: On the unification of two "maximal" axioms URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Martin's Maximum^{++} and Woodin's axiom (*) are two statements independent of, but consistent with, ZFC. I will present the common reasons they are appealing as set-theoretic axioms, before comparing the sense in which they are "maximal". I will also run through an exposition of the recent work by Aspero and Schindler, which shows Martin's Maximum^{++} implies (*), effectively "unifying" the statements.

Talk by Justin Moore this Friday (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

I sent an email instead of scheduling it, so I send the correct subject again to avoid confusion. Justin's talk will be this Friday.

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Justin Moore
Date and Time: Friday, February 26, 2021 - 1:30pm to 3:00pm
Title: On the additivity of strong homology for locally compact separable metric spaces
Abstract:
We show that it is consistent relative to a weakly compact cardinal that strong homology is additive and compactly supported within the class of locally compact separable metric spaces. This complements work of Mardešić and Prasolov showing that the Continuum Hypothesis implies that a countable sum of Hawaiian earrings witnesses the failure of strong homology to possess either of these properties. Our results build directly on work of Lambie-Hanson and the second author which establishes the consistency, relative to a weakly compact cardinal, of $\lim^{s}A=0$  for all $s\geq 1$ for a certain pro-abelian group $A$; we show that that work's arguments carry implications for the vanishing and additivity of the $\lim^{s}$ functors over a substantially more general class of pro-abelian groups indexed by $\mathbb{N}^{\mathbb{N}}$.

This is joint work with Nathaniel Bannister and Jeffrey Bergfalk.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk by Justin Moore this Friday (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Justin Moore
Date and Time: Friday, February 26, 2021 - 1:30pm to 3:00pm
Title: On the additivity of strong homology for locally compact separable metric spaces
Abstract:
We show that it is consistent relative to a weakly compact cardinal that strong homology is additive and compactly supported within the class of locally compact separable metric spaces. This complements work of Mardešić and Prasolov showing that the Continuum Hypothesis implies that a countable sum of Hawaiian earrings witnesses the failure of strong homology to possess either of these properties. Our results build directly on work of Lambie-Hanson and the second author which establishes the consistency, relative to a weakly compact cardinal, of $\lim^{s}A=0$  for all $s\geq 1$ for a certain pro-abelian group $A$; we show that that work's arguments carry implications for the vanishing and additivity of the $\lim^{s}$ functors over a substantially more general class of pro-abelian groups indexed by $\mathbb{N}^{\mathbb{N}}$.

This is joint work with Nathaniel Bannister and Jeffrey Bergfalk.


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk by Justin Moore tomorrow (1 30pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Justin Moore
Date and Time: Friday, February 26, 2021 - 1:30pm to 3:00pm
Title: On the additivity of strong homology for locally compact separable metric spaces
Abstract:
We show that it is consistent relative to a weakly compact cardinal that strong homology is additive and compactly supported within the class of locally compact separable metric spaces. This complements work of Mardešić and Prasolov showing that the Continuum Hypothesis implies that a countable sum of Hawaiian earrings witnesses the failure of strong homology to possess either of these properties. Our results build directly on work of Lambie-Hanson and the second author which establishes the consistency, relative to a weakly compact cardinal, of $\lim^{s}A=0$  for all $s\geq 1$ for a certain pro-abelian group $A$; we show that that work's arguments carry implications for the vanishing and additivity of the $\lim^{s}$ functors over a substantially more general class of pro-abelian groups indexed by $\mathbb{N}^{\mathbb{N}}$.

This is joint work with Nathaniel Bannister and Jeffrey Bergfalk.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:  Brent Cody (Virginia Commonwealth University)
TITLE: Higher indescribability and ideal operators
DATE: 24 February 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609


















Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:  Brent Cody (Virginia Commonwealth University)
TITLE: Higher indescribability and ideal operators
DATE: 24 February 2021
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.






Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609


















This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 22, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 22, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
SpeakerGraham Priest (CUNY) 

TitleSubstructural Solutions to the Semantic Paradoxes: a Dialetheic Perspective

 

AbstractOver the last decade or so, a number of writers have argued for  solutions to the paradoxes of semantic self-reference which proceed by dropping some of the structural rules of inference, most notably Cut and/or Contraction.  In this paper, we will examine such accounts, with a particular eye on their relationship to more familiar dialetheic accounts.

 


- - - - Tuesday, Feb 23, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Feb 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna

Independence in PA: The Method of (L,n)(L,n)-Models

The purpose of this talk is to exposit a method for proving independence over PA of 'mathematical' statements (whatever that means). The method uses the concept of an (L,n)(L,n)-model: a finite sequence of finite LL-structures for some first order LL extending the language of arithmetic. The idea is that this finite sequence is intended to represent increasing approximations of a potentially infinite structure and the machinery developed allows one to translate (meta-mathematical) compactness type statements, which are easily seen to be independent of PA, into statements about finite combinatorics, which have 'mathematical content'. (L,n)(L,n)-models were introduced by Shelah in the 70's in his alternative proof of the Paris-Harrington Theorem and also appears (implicitly) in his example of a true, unprovable Π01Π10 statement of some 'mathematical' content. A similar idea was discovered independently by Kripke (unpublished). In this talk we will flesh out the details of this method and extend the general theory. This will allow us to present, in a fairly systematic fashion, proofs of the Paris-Harrington Theorem and the independence over PA of several, similar, Ramsey Theoretic statements including some which are Π01Π10.



- - - - Wednesday, Feb 24, 2021 - - - -



- - - - Thursday, Feb 25, 2021 - - - -

Philog Seminar
Thursday, Feb 25, 6:30 PM
Rohit Parikh
Covid-19 and knowledge based computation

Abstract:  the purpose of this project is to combine insights from the logic of knowledge (act according to what you know), and graph theory (spread of infection follows the edges of a graph).  We show how knowledge based algorithms can be used to combine safety with economic and social activity.

A Zoom link will be posted on https://philog.arthurpaulpedersen.org/ 



- - - - Friday, Feb 26, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 26, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Farmer Schlutzenberg, University of Münster
(Non)uniqueness and (un)definability of embeddings beyond choice

Work in ZF and let j:VαVαj:Vα→Vα be an elementary, or partially elementary, embedding. One can examine the degree of uniqueness, definability or constructibility of jj. For example, is there β<αβ<α such that jj is the unique (partially) elementary extension of jVβj↾Vβ? Is jj definable from parameters over Vα? We will discuss some results along these lines, illustrating that answers can depend heavily on circumstances. Some of the work is due independently and earlier to Gabriel Goldberg.




Next Week in Logic at CUNY:

- - - - Monday, Mar 1, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Mar 1, 4.15-6.15 (NY time)
For meeting information, please email: yweiss@gradcenter.cuny.edu
Shay Logan (Kansas State)
Title: The Easy Argument Against Noncontractive Logics Doesn’t Work

Abstract: The Easy Argument against noncontractivism is the argument that essentially amounts to pointing out that contraction is just repeating oneself. The purpose of this talk is to explain why the Easy Argument fails. I show first that the Easy Argument fails by being insufficiently precise, since there are many ways we can combine premises in an argument. After correcting for this, the Easy Argument then fails by being straightforwardly invalid. The premises required to correct for *this* failure, however, have controversial consequences. Altogether, it seems arguments against noncontractive logics, if there are any, will be Hard—not Easy—Arguments.



- - - - Tuesday, Mar 2, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Mar 2, 7pm
The seminar will take place virtually at 7pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Ali Enayat, University of Gothenburg
PA with a class of indiscernibles

This talk focuses on the theory PAI (I for Indiscernibles), a theory formulated in the language of PA augmented with a unary predicate I(x). Models of PAI are of the form (M,I) where (1) M is a model of PA, (2) I is a proper class of M, i.e., I is unbounded in M and (M,I) satisfies PA*, and (3) I forms a class of indiscernibles over M. The formalizability of the Infinite Ramsey Theorem in PA makes it clear that PAI is a conservative extension of PA. As we will see, nonstandard models of PA (of any cardinality) that have an expansion to a model of PAI are precisely those nonstandard models PA that can carry an inductive partial satisfaction class. The formulation and investigation of PAI was inspired by my work on the set theoretical sibling ZFI of PAI, whose behavior I will also compare and contrast with that of PAI.



- - - - Wednesday, Mar 3, 2021 - - - -

The New York City Category Theory Seminar
For meeting zoom details email N. Yanofsky.
Date and Time:     Wednesday Mar 3, 2021, 7:00 - 8:30 PM., on Zoom.

Speaker:     Joshua Sussan, Medgar Evers, CUNY.

Title:    Categorification and quantum topology.


Abstract: The Jones polynomial of a link could be defined through the representation theory of quantum sl(2). It leads to a 3-manifold invariant and 2+1 dimensional TQFT. In the mid 1990s, Crane and Frenkel outlined the categorification program with the aim of constructing a 3+1 dimensional TQFT by upgrading the representation theory of quantum sl(2) to some categorical structures. We will review these ideas and give examples of various categorifications of quantum sl(2) constructions.




- - - - Thursday, Mar 4, 2021 - - - -



- - - - Friday, Mar 5, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Mar 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Hiroshi Sakai, Kobe University
Generalized stationary reflection and cardinal arithmetic

The stationary reflection principle, which is often called the Weak Reflection Principle, is known to have many interesting consequences. As for cardinal arithmetic, it implies that λω=λλω=λ for all regular cardinal λω2λ≥ω2. In this talk, we will discuss higher analogues of this stationary reflection principle and their consequences on cardinal arithmetic.


- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Talk by Assaf Rinot tomorrow (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Assaf Rinot
Date and Time: Friday, February 19, 2021 - 1:30pm to 3:00pm
Title: All colorings are strong - but some colorings are stronger than
the others.
Abstract: Strong colorings are everywhere - they can be obtained from
analysis of basis problems, transfinite diagonalizations, oscillations,
or walks on ordinals. They give rise to interesting topological spaces
and partial orders.
In this talk, I'll be looking at all aspects mentioned above, reporting
on findings from my joint projects with Kojman, Lambie-Hanson, Inamdar,
Steprans and Zhang.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER:  Hiroshi Sakai (Kobe University)
TITLE: Generalized Stationary Reflection and Cardinal Arithmetic
TIME: 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











Talk by Assaf Rinot Friday (1 30pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker : Assaf Rinot
Date and Time: Friday, February 19, 2021 - 1:30pm to 3:00pm
Title: All colorings are strong - but some colorings are stronger than
the others.
Abstract: Strong colorings are everywhere - they can be obtained from
analysis of basis problems, transfinite diagonalizations, oscillations,
or walks on ordinals. They give rise to interesting topological spaces
and partial orders.
In this talk, I'll be looking at all aspects mentioned above, reporting
on findings from my joint projects with Kojman, Lambie-Hanson, Inamdar,
Steprans and Zhang.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 15, 2021 - - - -



- - - - Tuesday, Feb 16, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Feb 16, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mateusz Łełyk, University of Warsaw
Nonequivalent axiomatizations of PAPA and the Tarski Boundary

We study a family of axioms expressingAll axioms of PA are true.' (*)‘All axioms of PA are true.' (*)where PA denotes Peano Arithmetic. More precisely, each such axiom states that all axioms from a chosen axiomatization of PA are true. We start with a very natural theory of truth CT(PA)CT−(PA) which is a finite extension of PA in the language of arithmetic augmented with a fresh predicate T to serve as a truth predicate for the language of arithmetic. Additional axioms of this theory are straightforward translations of inductive Tarski truth conditions. To study various possible ways of expressing (*), we investigate extensions of CT(PA)CT−(PA) with axioms of the formx(δ(x)T(x)).∀x(δ(x)→T(x)).In the above (and throughout the whole abstract) δ(x)δ(x) is an elementary formula which is proof-theoretically equivalent to the standard axiomatization of PA with the induction scheme, i.e. the equivalencex(Provδ(x)ProvPA(x)).∀x(Provδ(x)≡ProvPA(x)).is provable in IΣ1IΣ1. For every such δδ, the extension of CT(PA)CT−(PA) with the above axiom will be denoted CT[δ]CT−[δ].

In particular we shall focus on the arithmetical strength of theories CT[δ]CT−[δ]. The 'line' demarcating extensions of CT(PA)CT−(PA) which are conservative over PA from the nonconservative ones is known in the literature as the Tarski Boundary. For some time, there seemed to be the least (in terms of deductive strength) *natural* extension of CT(PA)CT−(PA) on the nonconservative side of the boundary, whose one axiomatization is given by CT(PA)CT−(PA) and Δ0Δ0 induction for the extended language (the theory is called CT0CT0). This theory can equivalently be axiomatized by adding to CT(PA)CT−(PA) the natural formal representation of the statement 'All theorems of PAPA are true.'. We show that the situation between the Tarski Boundary and CT0CT0 is much more interesting:

Theorem 1: For every r.e. theory Th in the language of arithmetic the following are equivalent:
1) CT0CT0⊢ Th
2) there exists δδ such that CT[δ]CT−[δ] and Th have the same arithmetical consequences.

Theorem 1 can be seen as a representation theorem for r.e. theories below REFω(PA)REFω(PA) (all finite iterations of uniform reflection over PAPA, which is the set of arithmetical consequences of CT0CT0): each such theory can be finitely axiomatized by a theory of the form CT[δ]CT−[δ], where δδ is proof-theoretically reducible to PAPA.

Secondly, we use theories CT[δ]CT−[δ] to investigate the situation below the Tarski Boundary. We shall prove the following result

Theorem 2: There exists a family {δf}fω<ω{δf}f∈ω<ω such that for all f,gω<ωf,g∈ω<ω
1) CT[δf]CT−[δf] is conservative over PAPA;
2) if fgf⊊g, then CT[δg]CT−[δg] properly extends CT[δf]CT−[δf];
3) if fgf⊥g then CT[δg]CT[δf]CT−[δg]∪CT−[δf] is nonconservative over PAPA (but consistent).






- - - - Wednesday, Feb 17, 2021 - - - -

The New York City Category Theory Seminar
Speaker:     Richard Blute, University of Ottawa.
Date and Time:     Wednesday February 17, 2021, 7:00 - 8:30 PM., on Zoom.
For meeting zoom details email N. Yanofsky.

Title:     Finiteness Spaces, Generalized Polynomial Rings and Topological Groupoids.


Abstract: The category of finiteness spaces was introduced by Thomas Ehrhard as a model of classical linear logic, where a set is equipped with a class of subsets to be thought of as finitary. Morphisms are relations preserving the finitary structure. The notion of finitary subset allows for a sharp analysis of computational structure.


Working with finiteness spaces forces the number of summands in certain calculations to be finite and thus avoid convergence questions. An excellent example of this is how Ribenboim’s theory of generalized power series rings can be naturally interpreted by assigning finiteness monoid structure to his partially ordered monoids. After Ehrhard’s linearization construction is applied, the resulting structures are the rings of Ribenboim’s construction.

There are several possible choices of morphism between finiteness spaces. If one takes structure-preserving partial functions, the resulting category is complete, cocomplete and symmetric monoidal closed. Using partial functions, we are able to model topological groupoids, when we consider composition as a partial function. We can associate to any hemicompact etale Hausdorff groupoid a complete convolution ring. This is in particular the case for the infinite paths groupoid associated to any countable row-finite directed graph.



- - - - Thursday, Feb 18, 2021 - - - -



- - - - Friday, Feb 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Philipp Lücke, University of Bonn

Magidor-style embedding characterizations of large cardinals

Motivated by a classical theorem of Magidor, I will present results providing characterizations of important objects from the lower end of the large cardinal hierarchy through the existence of elementary embeddings between set-sized models that map their critical point to the large cardinal in question. Focusing on the characterization of shrewd cardinals, introduced by Rathjen in a proof-theoretic context, I will show how these results can be used in the study of the combinatorics of strong chain conditions and the investigation of principles of structural reflection formulated by Bagaria.






Next Week in Logic at CUNY:

- - - - Monday, Feb 22, 2021 - - - -



- - - - Tuesday, Feb 23, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Feb 23, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Corey Switzer, University of Vienna


- - - - Wednesday, Feb 24, 2021 - - - -



- - - - Thursday, Feb 25, 2021 - - - -



- - - - Friday, Feb 26, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 26, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Farmer Schlutzenberg, University of Münster
(Non)uniqueness and (un)definability of embeddings beyond choice

Work in ZF and let j:VαVαj:Vα→Vα be an elementary, or partially elementary, embedding. One can examine the degree of uniqueness, definability or constructibility of jj. For example, is there β<αβ<α such that jj is the unique (partially) elementary extension of jVβj↾Vβ? Is jj definable from parameters over Vα? We will discuss some results along these lines, illustrating that answers can depend heavily on circumstances. Some of the work is due independently and earlier to Gabriel Goldberg.





- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

--------  ADMINISTRIVIA  --------

To subscribe/unsubscribe to this list, please email your request to jreitz@nylogic.org.

If you have a logic-related event that you would like included in future mailings, please email jreitz@nylogic.org

Logic Seminar 17 Feb 2021 17:00 hrs at NUS by Xiao Ming

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 17 February 2020, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Xiao Ming Title: Borel Order Dimensions URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Order dimension is a classical combinatorial object and has been widely studied by set theorists, combinatorists and computer scientists since its introduction by Dushnik and Miller in 1941. We focus on the partial orderings that are definable as a Borel subsets in a Polish space and analyze the order dimension that can be realized by Borel definable orders and show that there are some interesting behaviors that can be quite different from the classical order dimension using arbitrary realization. This is a joint work with Dilip Raghavan.

Upcoming CMU math logic events

Carnegie Mellon Logic Seminar
TUESDAY, February 16, 2021 Mathematical logic seminar:  3:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: The definable content of (co)homological invariants:  Cech cohomology ABSTRACT: In this talk we will develop a framework for enriching various classical invariants of homological algebra and algebraic topology with additional descriptive set-theoretic information. The resulting "definable invariants" can be used for much finer classification than their purely algebraic counterparts. We will then illustrate how these ideas apply to the classical Cech cohomology theory, by introducing a new invariant for locally compact metrizable spaces up to homotopy equivalence which we call "definable cohomology". In strong contrast to its classical counterpart, this definable cohomology theory provides complete classification to homotopy classes of mapping telescopes of d-tori, and for homotopy classes of maps from mapping telescopes of d-tori to spheres. The latter problem was raised in the d=1 case by Borsuk and Eilenberg in 1936. This is joint work with Jeffrey Bergfalk and Martino Lupini. TUESDAY, February 16, 2021 Set Theory Reading Group:  4:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ulam stability for quotients of abelian non-archimedean Polish groups ABSTRACT: Based on an earlier work of Shelah concerning the relationship of the continuum hypothesis to the cardinality of the set of automorphisms of $\mathcal{P}(\omega)/\mathrm{fin}$, Velickovic showed that if such an automorphism admits a Borel lift $\mathcal{P}(\omega)\to \mathcal{P}(\omega)$, then it is of a certain "trivial" form. Similarly, Kanovei and Reeken showed that if $N,M$ are countable dense subgroups of $\mathbb{R}$, then every homomorphism $\mathbb{R}/N\to \mathbb{R}/M$ with a Borel lift $\mathbb{R}\to \mathbb{R}$, is of a certain "trivial" form. Kanovei and Reeken asked whether quotients of the $p$-adic groups satisfy similar "Ulam stability" phenomena. In this talk, we will settle this question by providing Ulam-stability phenomena for definable homomorphisms $G/N\to H/M$ when $G,H$ are arbitrary abelian non-archimedean Polish groups and $N,M$ are Polishable subgroups. We will then illustrate how such rigidity results are in the heart of the definable cohomology theory which we developed in the previous talk. This is joint work with Jeffrey Bergfalk and Martino Lupini. THURSDAY, February 18, 2021 Model Theory Seminar:  10:00 A.M., Online, Michael Lieberman, Brno University of Technology Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Induced and higher-dimensional stable independence, Part I ABSTRACT: We introduce the notion of a stable independence relation on an abstract category, generalizing the notions familiar from classical and abstract model theory.  We discuss certain useful properties of such relations---chiefly, canonicity---and indicate that, in mu-AECs, the existence of a stable independence notion has the expected relationship with the failure of the order property.   We highlight an important special case, in which the category is derived by restricting to a nice family of morphisms in a larger, locally presentable category (e.g. R-modules with pure homomorphisms).  Here we find a surprisingly deep connection between the existence of a stable independence notion and the structure of the family of morphisms. Joint work with J. Rosický and S. Vasey. THURSDAY, February 25, 2021 Model Theory Seminar:  10:00 A.M., Online, Michael Lieberman, Brno University of Technology Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Induced and higher-dimensional stable independence, Part II ABSTRACT: We discuss the conditions under which a stable independence relation can be pushed upward---induced---from a subcategory to the category as a whole: namely, that the larger category is weakly stable and the subcategory is sufficiently nicely embedded.  While a model-theoretic argument can be given, we suggest that the category-theoretic analog is cleaner and more efficient. This has immediate applications: the algebraic classes considered in recent work of Mazari-Armida (torsion R-modules with pure monomorphisms, torsion-free Abelian groups with pure embeddings, etc.) all have weakly-stable independence notions.  Thanks to Mazari-Armida's results on Galois stability of such classes (and a few additional properties), it is clear that in each case the subcategory of sufficiently saturated objects has a stable independence notion: we conclude that the same holds of the categories themselves. Time permitting, we will also discuss the phenomenon of excellence---that is, the existence of stable independence in all dimensions---in this context.  As it happens, in any category of the special form considered in Part I (obtained by restricting to a nice class of morphisms in a nice category), excellence follows directly from the existence of a stable independence notion. Joint work with J. Rosický and S. Vasey. TUESDAY, March 2, 2021 Mathematical logic seminar:  3:30 P.M., Online, Marc Noy, Technical University of Catalonia Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Zero-One and Convergence Laws for Graphs Embeddable on a Fixed Surface ABSTRACT: Let G be a class of labeled graphs with the uniform probability distribution on graphs with a fixed number of vertices. Given a graph property A, we are interested in the limiting probability that A holds in G. It was shown by Heinig et al. that this limiting probability always exists when G is the class of planar graphs and A is any property expressible in monadic second order logic (MSO), and it was conjectured that the same result holds for the class of graphs embeddable on a fixed surface S. After reviewing the results for planar graphs, and more generally for minor-closed classes of graphs, we will refute the conjecture by showing that for every closed surface (orientable or not) other than the sphere there exists an MSO graph property whose limiting probability does not exist. In addition we show that every rational number in [0,1] is the limiting probability of some MSO property, as opposed to the class of planar graphs where there are so-called gaps. The proof relies on a combination of methods from structural graph theory, concretely large face-width embeddings of graphs on surfaces, analytic combinatorics, and finite model theory. This is joint work with Albert Atserias and Stephan Kreutzer. TUESDAY, April 20, 2021 Mathematical logic seminar:  3:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA TUESDAY, April 20, 2021 Set Theory Reading Group:  4:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA

Upcoming math logic events at CMU

Carnegie Mellon Logic Seminar
TUESDAY, February 9, 2021 Mathematical logic seminar:  3:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Order-preserving Martin’s Conjecture ABSTRACT: Martin’s Conjecture is a precise way of asserting that, up to equivalence, the only natural functions on the Turing degrees are the familiar ones: the constant functions, the identity, the Turing jump, and the transfinite iterates of the Turing jump. This conjecture is open even restricted to low-level Borel functions, but there have been partial results over the years which show it holds for classes of functions meeting requirements orthogonal to definability. Our recent result is that part of Martin’s Conjecture (lately called “part one”) holds for the class of order-preserving functions. In particular, it follows that the full Martin’s Conjecture holds for Borel order-preserving functions. We’ll talk about Martin’s Conjecture broadly and say something about this recent work. This is joint work with Patrick Lutz. TUESDAY, February 9, 2021 Set Theory Reading Group:  4:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Measure-preserving functions on the Turing degrees ABSTRACT: One proof of part one of Martin’s Conjecture for order-preserving functions works for a bigger class of functions: those which are measure-preserving for the Martin measure, in the sense of ergodic theory. Looking at this class of functions brings out more set-theoretic aspects of Martin’s Conjecture. For example, part one of Martin’s Conjecture is equivalent to the non-existence of other non-principal ultrafilters on the Turing degrees Rudin-Keisler below the Martin measure. We’ll talk about the proof of part one of Martin’s Conjecture for this class of functions and some consequences. This is joint work with Patrick Lutz. THURSDAY, February 11, 2021 Model Theory Seminar:  10:00 A.M., Online, John Baldwin, UIC Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: The Hanf number for extendability is the first measurable cardinal, Part 2 ABSTRACT: We prove  in ZFC the existence of a  complete sentence of infinitary logic  that has maximal models in a set of cardinals cofinal in the first measurable but no maximal models in any  cardinal beyond the first measurable. As a warmup to the first lecture please look at the Motivation http://homepages.math.uic.edu/~jbaldwin/pub/cmupre This is joint work with Saharon Shelah. Preprints are available at  http://homepages.math.uic.edu/~jbaldwin/pub/ahanfmaxjan21.pdf and http://homepages.math.uic.edu/~jbaldwin/pub/ahazfjan7.pdf TUESDAY, February 16, 2021 Mathematical logic seminar:  3:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: The definable content of (co)homological invariants:  Cech cohomology ABSTRACT: In this talk we will develop a framework for enriching various classical invariants of homological algebra and algebraic topology with additional descriptive set-theoretic information. The resulting "definable invariants" can be used for much finer classification than their purely algebraic counterparts. We will then illustrate how these ideas apply to the classical Cech cohomology theory, by introducing a new invariant for locally compact metrizable spaces up to homotopy equivalence which we call "definable cohomology". In strong contrast to its classical counterpart, this definable cohomology theory provides complete classification to homotopy classes of mapping telescopes of d-tori, and for homotopy classes of maps from mapping telescopes of d-tori to spheres. The latter problem was raised in the d=1 case by Borsuk and Eilenberg in 1936. This is joint work with Jeffrey Bergfalk and Martino Lupini. TUESDAY, February 16, 2021 Set Theory Reading Group:  4:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ulam stability for quotients of abelian non-archimedean Polish groups ABSTRACT: Based on an earlier work of Shelah concerning the relationship of the continuum hypothesis to the cardinality of the set of automorphisms of $\mathcal{P}(\omega)/\mathrm{fin}$, Velickovic showed that if such an automorphism admits a Borel lift $\mathcal{P}(\omega)\to \mathcal{P}(\omega)$, then it is of a certain "trivial" form. Similarly, Kanovei and Reeken showed that if $N,M$ are countable dense subgroups of $\mathbb{R}$, then every homomorphism $\mathbb{R}/N\to \mathbb{R}/M$ with a Borel lift $\mathbb{R}\to \mathbb{R}$, is of a certain "trivial" form. Kanovei and Reeken asked whether quotients of the $p$-adic groups satisfy similar "Ulam stability" phenomena. In this talk, we will settle this question by providing Ulam-stability phenomena for definable homomorphisms $G/N\to H/M$ when $G,H$ are arbitrary abelian non-archimedean Polish groups and $N,M$ are Polishable subgroups. We will then illustrate how such rigidity results are in the heart of the definable cohomology theory which we developed in the previous talk. This is joint work with Jeffrey Bergfalk and Martino Lupini. THURSDAY, February 25, 2021 Model Theory Seminar:  10:00 A.M., Online, Michael Lieberman, Brno University of Technology Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Induced and higher-dimensional stable independence, Part I ABSTRACT: We introduce the notion of a stable independence relation on an abstract category, generalizing the notions familiar from classical and abstract model theory.  We discuss certain useful properties of such relations---chiefly, canonicity---and indicate that, in mu-AECs, the existence of a stable independence notion has the expected relationship with the failure of the order property.   We highlight an important special case, in which the category is derived by restricting to a nice family of morphisms in a larger, locally presentable category (e.g. R-modules with pure homomorphisms).  Here we find a surprisingly deep connection between the existence of a stable independence notion and the structure of the family of morphisms. Joint work with J. Rosický and S. Vasey. TUESDAY, March 2, 2021 Mathematical logic seminar:  3:30 P.M., Online, Marc Noy, Technical University of Catalonia Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Zero-One and Convergence Laws for Graphs Embeddable on a Fixed Surface ABSTRACT: Let G be a class of labeled graphs with the uniform probability distribution on graphs with a fixed number of vertices. Given a graph property A, we are interested in the limiting probability that A holds in G. It was shown by Heinig et al. that this limiting probability always exists when G is the class of planar graphs and A is any property expressible in monadic second order logic (MSO), and it was conjectured that the same result holds for the class of graphs embeddable on a fixed surface S. After reviewing the results for planar graphs, and more generally for minor-closed classes of graphs, we will refute the conjecture by showing that for every closed surface (orientable or not) other than the sphere there exists an MSO graph property whose limiting probability does not exist. In addition we show that every rational number in [0,1] is the limiting probability of some MSO property, as opposed to the class of planar graphs where there are so-called gaps. The proof relies on a combination of methods from structural graph theory, concretely large face-width embeddings of graphs on surfaces, analytic combinatorics, and finite model theory. This is joint work with Albert Atserias and Stephan Kreutzer. THURSDAY, March 4, 2021 Model Theory Seminar:  10:00 A.M., Online, Michael Lieberman, Brno University of Technology Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: Induced and higher-dimensional stable independence, Part II ABSTRACT: We discuss the conditions under which a stable independence relation can be pushed upward---induced---from a subcategory to the category as a whole: namely, that the larger category is weakly stable and the subcategory is sufficiently nicely embedded.  While a model-theoretic argument can be given, we suggest that the category-theoretic analog is cleaner and more efficient. This has immediate applications: the algebraic classes considered in recent work of Mazari-Armida (torsion R-modules with pure monomorphisms, torsion-free Abelian groups with pure embeddings, etc.) all have weakly-stable independence notions.  Thanks to Mazari-Armida's results on Galois stability of such classes (and a few additional properties), it is clear that in each case the subcategory of sufficiently saturated objects has a stable independence notion: we conclude that the same holds of the categories themselves. Time permitting, we will also discuss the phenomenon of excellence---that is, the existence of stable independence in all dimensions---in this context.  As it happens, in any category of the special form considered in Part I (obtained by restricting to a nice class of morphisms in a nice category), excellence follows directly from the existence of a stable independence notion. Joint work with J. Rosický and S. Vasey. TUESDAY, April 20, 2021 Mathematical logic seminar:  3:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA TUESDAY, April 20, 2021 Set Theory Reading Group:  4:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 8, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 8, 4.15-6.15 (NY time) 
For meeting information, please email: yweiss@gradcenter.cuny.edu 
Patrick Girard, Auckland
Title: Classical Counterpossibles

Abstract: We present four classical theories of counterpossibles that combine modalities and counterfactuals. Two theories are anti-vacuist and forbid vacuously true counterfactuals, two are quasi-vacuist and allow counterfactuals to be vacuously true when their antecedent is not only impossible, but also inconceivable. The theories vary on how they restrict the interaction of modalities and counterfactuals. We provide a logical cartography with precise acceptable boundaries, illustrating to what extent nonvacuism about counterpossibles can be reconciled with classical logic.

Note: this is joint work with Rohan French (UC Davis) and Dave Ripley (Monash).

 



- - - - Tuesday, Feb 9, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Feb 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Leszek Kołodziejczyk, University of Warsaw


An isomorphism theorem for models of Weak Kőnig's Lemma without induction

We prove that any two countable models of the theory WKL0WKL0∗ sharing the same first-order universe and containing the same counterexample to Σ01Σ10 induction are isomorphic.

This theorem implies that over WKL0+¬IΣ01WKL0∗+¬IΣ10, the analytic hierarchy collapses to the arithmetic hierarchy. It also implies that WKL0WKL0∗ is the strongest Π12Π21 statement that is Π11Π11-conservative over RCA0+¬IΣ01RCA0∗+¬IΣ10. Together with the (slightly subtle) generalizations of the theorem to higher levels of the arithmetic hierarchy, this gives an 'almost negative' answer to a question of Towsner, who asked whether Π11Π11-conservativity of Π12Π21 sentences over collection principles is a Π02Π20-complete computational problem. Our results also have some implications for the reverse mathematics of combinatorial principles: for instance, we get a specific Π11Π11 sentence that is provable in RCA0+BΣ02RCA0+BΣ20 exactly if the Π11Π11 consequences of RCA0+RT22RCA0+RT22 coincide with BΣ02BΣ20.

On the side, we also give a positive answer to Towsner's question as originally stated.

Joint work with Marta Fiori Carones, Tin Lok Wong, and Keita Yokoyama.





- - - - Wednesday, Feb 10, 2021 - - - -

The New York City Category Theory Seminar
Speaker:     Peter Hines University of York.

Date and Time:     Wednesday February 10, 2021, 7:00 - 8:30 PM., on Zoom.

For meeting zoom details email N. Yanofsky.

Title:    Shuffling cards as an operad.


Abstract: The theory of how two packs of cards may be shuffled together to form a single pack has been remarkably well-studied in combinatorics, group theory, statistics, and other areas of mathematics. This talk aims to study natural extensions where 1/ We may have infinitely many cards in a deck, 2/ We may take the result of a previous shuffle as one of our decks of cards (i.e. shuffles are hierarchical), and 3/ There may even be an infinite number of decks of cards.


Far from being 'generalisation for generalisation's sake', the original motivation came from theoretical & practical computer science. The mathematics of card shuffles is commonly used to describe processing in multi-threaded computations. Moving to the infinite case gives a language in which one may talk about potentially non-terminating processes, or servers with an unbounded number of clients, etc.

However, this talk is entirely about algebra & category theory -- just as in the finite case, the mathematics is of interest in its own right, and should be studied as such.

We model shuffles using operads. The intuition behind them of allowing for arbitrary n-ary operations that compose in a hierarchical manner makes them a natural, inevitable choice for describing such processes such as merging multiple packs of cards.

We use very concrete examples, based on endomorphism operads in groupoids of arithmetic operations. The resulting structures are at the same time both simple (i.e. elementary arithmetic operations), and related to deep structures in mathematics and category theory (topologies, tensors, coherence, associahedra, etc.)

We treat this as a feature, not a bug, and use it to describe complex structures in elementary terms. We also aim to give previously unobserved connections between distinct areas of mathematics.





- - - - Thursday, Feb 11, 2021 - - - -

Philog Seminar
Thursday February 11, 6:30 PM
A Zoom link will be posted on philog.arthurpaulpedersen.org 
Jayant Shah, Mathematics Department, Northeastern University
The Aumann Maschler paper on the Game theoretic analysis of a bankruptcy problem from the Talmud


- - - - Friday, Feb 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 12, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Bea Adam-Day, University of Leeds

Indestructibility (or otherwise) of subcompactness and C(n)-supercompactness

Indestructibility results of large cardinals have been an area of interest since Laver's 1978 proof that the supercompactness of κκ may be made indestructible by any <κ-directed closed forcing. I will present a continuation of this work, showing that αα-subcompact cardinals may be made suitably indestructible, but that for C(n)-supercompact cardinals this is largely not possible.





Next Week in Logic at CUNY:

- - - - Monday, Feb 15, 2021 - - - -



- - - - Tuesday, Feb 16, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Tuesday, Feb 16, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Mateusz Łełyk, University of Warsaw
Nonequivalent axiomatizations of PAPA and the Tarski Boundary

We study a family of axioms expressingAll axioms of PA are true.' (*)‘All axioms of PA are true.' (*)where PA denotes Peano Arithmetic. More precisely, each such axiom states that all axioms from a chosen axiomatization of PA are true. We start with a very natural theory of truth CT(PA)CT−(PA) which is a finite extension of PA in the language of arithmetic augmented with a fresh predicate T to serve as a truth predicate for the language of arithmetic. Additional axioms of this theory are straightforward translations of inductive Tarski truth conditions. To study various possible ways of expressing (*), we investigate extensions of CT(PA)CT−(PA) with axioms of the formx(δ(x)T(x)).∀x(δ(x)→T(x)).In the above (and throughout the whole abstract) δ(x)δ(x) is an elementary formula which is proof-theoretically equivalent to the standard axiomatization of PA with the induction scheme, i.e. the equivalencex(Provδ(x)ProvPA(x)).∀x(Provδ(x)≡ProvPA(x)).is provable in IΣ1IΣ1. For every such δδ, the extension of CT(PA)CT−(PA) with the above axiom will be denoted CT[δ]CT−[δ].

In particular we shall focus on the arithmetical strength of theories CT[δ]CT−[δ]. The 'line' demarcating extensions of CT(PA)CT−(PA) which are conservative over PA from the nonconservative ones is known in the literature as the Tarski Boundary. For some time, there seemed to be the least (in terms of deductive strength) *natural* extension of CT(PA)CT−(PA) on the nonconservative side of the boundary, whose one axiomatization is given by CT(PA)CT−(PA) and Δ0Δ0 induction for the extended language (the theory is called CT0CT0). This theory can equivalently be axiomatized by adding to CT(PA)CT−(PA) the natural formal representation of the statement 'All theorems of PAPA are true.'. We show that the situation between the Tarski Boundary and CT0CT0 is much more interesting:

Theorem 1: For every r.e. theory Th in the language of arithmetic the following are equivalent:
1) CT0CT0⊢ Th
2) there exists δδ such that CT[δ]CT−[δ] and Th have the same arithmetical consequences.

Theorem 1 can be seen as a representation theorem for r.e. theories below REFω(PA)REFω(PA) (all finite iterations of uniform reflection over PAPA, which is the set of arithmetical consequences of CT0CT0): each such theory can be finitely axiomatized by a theory of the form CT[δ]CT−[δ], where δδ is proof-theoretically reducible to PAPA.

Secondly, we use theories CT[δ]CT−[δ] to investigate the situation below the Tarski Boundary. We shall prove the following result

Theorem 2: There exists a family {δf}fω<ω{δf}f∈ω such that for all f,gω<ωf,g∈ω
1) CT[δf]CT−[δf] is conservative over PAPA;
2) if fgf⊊g, then CT[δg]CT−[δg] properly extends CT[δf]CT−[δf];
3) if fgf⊥g then CT[δg]CT[δf]CT−[δg]∪CT−[δf] is nonconservative over PAPA (but consistent).






- - - - Wednesday, Feb 17, 2021 - - - -

The New York City Category Theory Seminar
Speaker:     Richard Blute, University of Ottawa.
Date and Time:     Wednesday February 17, 2021, 7:00 - 8:30 PM., on Zoom.
For meeting zoom details email N. Yanofsky.

Title:     Finiteness Spaces, Generalized Polynomial Rings and Topological Groupoids.


Abstract: The category of finiteness spaces was introduced by Thomas Ehrhard as a model of classical linear logic, where a set is equipped with a class of subsets to be thought of as finitary. Morphisms are relations preserving the finitary structure. The notion of finitary subset allows for a sharp analysis of computational structure.


Working with finiteness spaces forces the number of summands in certain calculations to be finite and thus avoid convergence questions. An excellent example of this is how Ribenboim’s theory of generalized power series rings can be naturally interpreted by assigning finiteness monoid structure to his partially ordered monoids. After Ehrhard’s linearization construction is applied, the resulting structures are the rings of Ribenboim’s construction.

There are several possible choices of morphism between finiteness spaces. If one takes structure-preserving partial functions, the resulting category is complete, cocomplete and symmetric monoidal closed. Using partial functions, we are able to model topological groupoids, when we consider composition as a partial function. We can associate to any hemicompact etale Hausdorff groupoid a complete convolution ring. This is in particular the case for the infinite paths groupoid associated to any countable row-finite directed graph.



- - - - Thursday, Feb 18, 2021 - - - -



- - - - Friday, Feb 19, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 19, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Philipp Lücke, University of Bonn
TBA

- - - - Other Logic News - - - -



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Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER: Matteo Viale (Università di Torino)
TITLE: The  model-companionship spectrum of set theory, generic absoluteness, and the continuum problem.
TIME: February 10 at 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.











Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609
























Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











Talk by Andrés Villaveces tomorrow (1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker :Andrés Villaveces, Universidad Nacional de Colombia
Date and Time: Friday, February 5, 2021 - 1:30pm to 3:00pm
Title: Axiomatizations of abstract elementary classes and natural logics for model theory: the role of partition relations.
Abstract:
Two seemingly unrelated questions (the quest for natural logics of abstract elementary classes on the one hand, and the quest for logics adequate to model theory on the other hand) converge around the same combinatorial core: partition relations for scattered order types (due to Kómjath and Shelah). I will present recent results concerning the first question (and axiomatizing a.e.c.'s - joint work with Shelah) and the second question (joint work with Väänänen).

Bio: Andrés Villaveces is a mathematician, working at Universidad Nacional de Colombia in Bogotá. Villaveces earned his doctoral degree from the University of Wisconsin-Madison in 1996 under the supervision of Ken Kunen. He held a postdoctoral position at the Hebrew University of Jerusalem (1996-1997) and has been a visiting professor at Carnegie Mellon University (2002-2003) and at the University of Helsinki (2007 and 2015). His work centers on the model theory of Abstract Elementary Classes and its connections with set theory and other parts of logic and mathematics.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Talk by Andrés Villaveces Friday ( 1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker :Andrés Villaveces, Universidad Nacional de Colombia
Date and Time: Friday, February 5, 2021 - 1:30pm to 3:00pm
Title: Axiomatizations of abstract elementary classes and natural logics for model theory: the role of partition relations.
Abstract:
Two seemingly unrelated questions (the quest for natural logics of abstract elementary classes on the one hand, and the quest for logics adequate to model theory on the other hand) converge around the same combinatorial core: partition relations for scattered order types (due to Kómjath and Shelah). I will present recent results concerning the first question (and axiomatizing a.e.c.'s - joint work with Shelah) and the second question (joint work with Väänänen).

Bio: Andrés Villaveces is a mathematician, working at Universidad Nacional de Colombia in Bogotá. Villaveces earned his doctoral degree from the University of Wisconsin-Madison in 1996 under the supervision of Ken Kunen. He held a postdoctoral position at the Hebrew University of Jerusalem (1996-1997) and has been a visiting professor at Carnegie Mellon University (2002-2003) and at the University of Helsinki (2007 and 2015). His work centers on the model theory of Abstract Elementary Classes and its connections with set theory and other parts of logic and mathematics.


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Feb 1, 2021 - - - -



- - - - Tuesday, Feb 2, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Wednesday, Feb 2, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

James Walsh, Cornell University
Reducing omega-model reflection to iterated syntactic reflection

Two types of principles are commonly called “reflection principles” in reverse mathematics. According to syntactic reflection principles for T, every theorem of T (from some complexity class) is true. According to semantic reflection principles, every set belongs to some (sufficiently correct) model of T. We will present a connection between syntactic reflection and semantic reflection in second-order arithmetic: for any Pi^1_2 axiomatized theory T, every set is contained in an omega model of T if and only if every iteration of Pi^1_1 reflection for T along a well-ordering is Pi^1_1 sound. There is a thorough proof-theoretic understanding of the latter in terms of ordinal analysis. Accordingly, these reductions yield proof-theoretic analyses of omega-model reflection principles. This is joint work with Fedor Pakhomov.



- - - - Wednesday, Feb 3, 2021 - - - -

The New York City Category Theory Seminar
Speaker:     Jason Parker, Brandon University in Manitoba.

Date and Time:     Wednesday February 3, 2021, 7:00 - 8:30 PM., on Zoom.

For meeting zoom details email N. Yanofsky.

Title:    Isotropy Groups of Quasi-Equational Theories.

Abstract: In [2], my PhD supervisors (Pieter Hofstra and Philip Scott) and I studied the new topos-theoretic phenomenon of isotropy (as introduced in [1]) in the context of single-sorted algebraic theories, and we gave a logical/syntactic characterization of the isotropy group of any such theory, thereby showing that it encodes a notion of inner automorphism or conjugation for the theory. In the present talk, I will summarize the results of my recent PhD thesis, in which I build on this earlier work by studying the isotropy groups of (multi-sorted) quasi-equational theories (also known as essentially algebraic, cartesian, or finite limit theories). In particular, I will show how to give a logical/syntactic characterization of the isotropy group of any such theory, and that it encodes a notion of inner automorphism or conjugation for the theory. I will also describe how I have used this characterization to exactly characterize the ‘inner automorphisms’ for several different examples of quasi-equational theories, most notably the theory of strict monoidal categories and the theory of presheaves valued in a category of models. In particular, the latter example provides a characterization of the (covariant) isotropy group of a category of set-valued presheaves, which had been an open question in the theory of categorical isotropy.

[1] J. Funk, P. Hofstra, B. Steinberg. Isotropy and crossed toposes. Theory and Applications of Categories 26, 660-709, 2012.

[2] P. Hofstra, J. Parker, P.J. Scott. Isotropy of algebraic theories. Electronic Notes in Theoretical Computer Science 341, 201-217, 2018.




- - - - Thursday, Feb 4, 2021 - - - -



- - - - Friday, Feb 5, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Andreas Blass, University of Michigan
Choice from Finite Sets: A Topos View

Tarski proved (but didn't publish) the theorem that choice from pairs implies choice from four-element sets. Mostowski (1937) began a systematic study of such implications between choice axioms for families of finite sets. Gauntt (1970) completed that study (but didn't publish the results), obtaining equivalent characterizations in terms of fixed points of permutation groups. Truss (1973) extended Gauntt's results (and published this work).

It turns out that these finite choice axioms and their group-theoretic characterizations are instances of the same topos-theoretic statements, interpreted in two very different classes of topoi. My main result is an extension of that observation to the class of all topoi.

Most of my talk will be explaining the background: finite choice axioms, permutation groups, and a little bit about topoi - just enough to make sense of the main result. If time permits, I'll describe some of the ingredients of the proof.






Next Week in Logic at CUNY:

- - - - Monday, Feb 8, 2021 - - - -

Logic and Metaphysics Workshop
Date: Monday, Feb 8, 4.15-6.15 (NY time) 
For meeting information, please email: yweiss@gradcenter.cuny.edu 
Patrick Girard, Auckland



- - - - Tuesday, Feb 9, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Wednesday, Feb 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Leszek Kołodziejczyk, University of Warsaw


An isomorphism theorem for models of Weak Kőnig's Lemma without induction

We prove that any two countable models of the theory WKL0WKL0∗ sharing the same first-order universe and containing the same counterexample to Σ01Σ10 induction are isomorphic.

This theorem implies that over WKL0+¬IΣ01WKL0∗+¬IΣ10, the analytic hierarchy collapses to the arithmetic hierarchy. It also implies that WKL0WKL0∗ is the strongest Π12Π21 statement that is Π11Π11-conservative over RCA0+¬IΣ01RCA0∗+¬IΣ10. Together with the (slightly subtle) generalizations of the theorem to higher levels of the arithmetic hierarchy, this gives an 'almost negative' answer to a question of Towsner, who asked whether Π11Π11-conservativity of Π12Π21 sentences over collection principles is a Π02Π20-complete computational problem. Our results also have some implications for the reverse mathematics of combinatorial principles: for instance, we get a specific Π11Π11 sentence that is provable in RCA0+BΣ02RCA0+BΣ20 exactly if the Π11Π11 consequences of RCA0+RT22RCA0+RT22 coincide with BΣ02BΣ20.

On the side, we also give a positive answer to Towsner's question as originally stated.

Joint work with Marta Fiori Carones, Tin Lok Wong, and Keita Yokoyama.





- - - - Wednesday, Feb 10, 2021 - - - -

The New York City Category Theory Seminar
Speaker:     Peter Hines University of York.

Date and Time:     Wednesday February 10, 2021, 7:00 - 8:30 PM., on Zoom.

For meeting zoom details email N. Yanofsky.

Title:    Invertibility in Operads : an elementary arithmetic approach.


Abstract: This talk is motivated by two areas of 'lost mathematics' -- topics where it is clear that interesting theory was once known & understood, but only incomplete traces remain in the historical record. One of these was due to ancient Greek mathematicians & logicians, and the other is a much lesser-known relation of a famous open problem from the 20th century.

One objective of this talk is to trace a link between the two. However, this is not an exercise in the 'History of Mathematics' -- the connections rely on theory that certainly was not understood in either time period.

Precisely, we consider 'Invertible Operads' -- that is, those whose composition operations are either partially or globally invertible. We look at examples that are freely generated by some given set of operations, with particular reference to those whose composition operations may be given by elementary arithmetic functions.

We demonstrate how such structures arise in a range of different topics, providing previously unobserved connections between them. This includes subjects such as standard Young tableaux, mixed-radix counting systems, topologies on the natural numbers, logical models, famous groups, and combinatorially-inspired polyhedra.

This is very much work in progress, and aims to present interesting questions as much as interesting structures and results.





- - - - Thursday, Feb 11, 2021 - - - -



- - - - Friday, Feb 12, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 12, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Bea Adam-Day, University of Leeds



- - - - Other Logic News - - - -



- - - - Web Site - - - -

"Find us on the web at:  nylogic.github.io
(site designed, built & maintained by Victoria Gitman)"

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Barcelona Set theory Seminar

Barcelona Logic Seminar

Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER: Adrian Mathias (Université de la Réunion)
TITLE: Power-admissible sets and ill-founded omega-models of weak subsystems of ZFC
TIME: February 3 at 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.









Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609























CMU events starting next week

Carnegie Mellon Logic Seminar
TUESDAY, February 2, 2021 Mathematical logic seminar: 3:30 P.M., Online, Anush Tserunyan, McGill University Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ergodic theorems along trees ABSTRACT: In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in front of the point $x$. We prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of T that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields forward ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank, where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. This strengthens Bufetov’s theorem from 2000, which was the most general result in this vein. This is joint work with Jenna Zomback. TUESDAY, February 2, 2021 Set Theory Reading Group: 4:30 P.M., Online, Jenna Zomback, University of Illinois at Urbana-Champaign Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ergodic theorems along trees: the proofs ABSTRACT: In this continuation of the previous talk, we discuss a backward (inverse) ergodic theorem for a probability measure preserving (pmp) transformation $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). We will derive from it a new (forward) pointwise ergodic theorem for pmp actions of free groups of finite rank, where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. We will then discuss a very short proof (due to Tserunyan) of the classical pointwise ergodic theorem, and, using this proof as an outline, we will sketch the proof of the backward ergodic theorem. This is joint work with Anush Tserunyan. THURSDAY, February 4, 2021 Model Theory Seminar: 10:00 A.M., Online, John Baldwin, UIC Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: The Hanf number for extendability is the first measurable cardinal, Part 1 ABSTRACT: We prove in ZFC the existence of a complete sentence of infinitary logic that has maximal models in a set of cardinals cofinal in the first measurable but no maximal models in any cardinal beyond the first measurable. As a warmup to the first lecture please look at the Motivation http://homepages.math.uic.edu/~jbaldwin/pub/cmupre This is joint work with Saharon Shelah. Preprints are available at http://homepages.math.uic.edu/~jbaldwin/pub/ahanfmaxjan21.pdf and http://homepages.math.uic.edu/~jbaldwin/pub/ahazfjan7.pdf TUESDAY, February 9, 2021 Mathematical logic seminar: 3:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Order-preserving Martin’s Conjecture ABSTRACT: Martin’s Conjecture is a precise way of asserting that, up to equivalence, the only natural functions on the Turing degrees are the familiar ones: the constant functions, the identity, the Turing jump, and the transfinite iterates of the Turing jump. This conjecture is open even restricted to low-level Borel functions, but there have been partial results over the years which show it holds for classes of functions meeting requirements orthogonal to definability. Our recent result is that part of Martin’s Conjecture (lately called “part one”) holds for the class of order-preserving functions. In particular, it follows that the full Martin’s Conjecture holds for Borel order-preserving functions. We’ll talk about Martin’s Conjecture broadly and say something about this recent work. This is joint work with Patrick Lutz. TUESDAY, February 9, 2021 Set Theory Reading Group: 4:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Measure-preserving functions on the Turing degrees ABSTRACT: One proof of part one of Martin’s Conjecture for order-preserving functions works for a bigger class of functions: those which are measure-preserving for the Martin measure, in the sense of ergodic theory. Looking at this class of functions brings out more set-theoretic aspects of Martin’s Conjecture. For example, part one of Martin’s Conjecture is equivalent to the non-existence of other non-principal ultrafilters on the Turing degrees Rudin-Keisler below the Martin measure. We’ll talk about the proof of part one of Martin’s Conjecture for this class of functions and some consequences. This is joint work with Patrick Lutz. THURSDAY, February 11, 2021 Model Theory Seminar: 10:00 A.M., Online, John Baldwin, UIC Join Zoom Meeting: https://cmu.zoom.us/j/96301869290?pwd=Qk1zS0h6ZThmUnRpbmNLNkVJSjkrQT09 Meeting ID: 963 0186 9290 Passcode: 567655 TITLE: The Hanf number for extendability is the first measurable cardinal, Part 2 ABSTRACT: We prove in ZFC the existence of a complete sentence of infinitary logic that has maximal models in a set of cardinals cofinal in the first measurable but no maximal models in any cardinal beyond the first measurable. As a warmup to the first lecture please look at the Motivation http://homepages.math.uic.edu/~jbaldwin/pub/cmupre This is joint work with Saharon Shelah. Preprints are available at http://homepages.math.uic.edu/~jbaldwin/pub/ahanfmaxjan21.pdf and http://homepages.math.uic.edu/~jbaldwin/pub/ahazfjan7.pdf TUESDAY, February 16, 2021 Mathematical logic seminar: 3:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: The definable content of (co)homological invariants: Cech cohomology ABSTRACT: In this talk we will develop a framework for enriching various classical invariants of homological algebra and algebraic topology with additional descriptive set-theoretic information. The resulting "definable invariants" can be used for much finer classification than their purely algebraic counterparts. We will then illustrate how these ideas apply to the classical Cech cohomology theory, by introducing a new invariant for locally compact metrizable spaces up to homotopy equivalence which we call "definable cohomology". In strong contrast to its classical counterpart, this definable cohomology theory provides complete classification to homotopy classes of mapping telescopes of d-tori, and for homotopy classes of maps from mapping telescopes of d-tori to spheres. The latter problem was raised in the d=1 case by Borsuk and Eilenberg in 1936. This is joint work with Jeffrey Bergfalk and Martino Lupini. TUESDAY, February 16, 2021 Set Theory Reading Group: 4:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ulam stability for quotients of abelian non-archimedean Polish groups ABSTRACT: Based on an earlier work of Shelah concerning the relationship of the continuum hypothesis to the cardinality of the set of automorphisms of $\mathcal{P}(\omega)/\mathrm{fin}$, Velickovic showed that if such an automorphism admits a Borel lift $\mathcal{P}(\omega)\to \mathcal{P}(\omega)$, then it is of a certain "trivial" form. Similarly, Kanovei and Reeken showed that if $N,M$ are countable dense subgroups of $\mathbb{R}$, then every homomorphism $\mathbb{R}/N\to \mathbb{R}/M$ with a Borel lift $\mathbb{R}\to \mathbb{R}$, is of a certain "trivial" form. Kanovei and Reeken asked whether quotients of the $p$-adic groups satisfy similar "Ulam stability" phenomena. In this talk, we will settle this question by providing Ulam-stability phenomena for definable homomorphisms $G/N\to H/M$ when $G,H$ are arbitrary abelian non-archimedean Polish groups and $N,M$ are Polishable subgroups. We will then illustrate how such rigidity results are in the heart of the definable cohomology theory which we developed in the previous talk. This is joint work with Jeffrey Bergfalk and Martino Lupini. TUESDAY, March 2, 2021 Mathematical logic seminar: 3:30 P.M., Online, Marc Noy, Technical University of Catalonia Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Zero-One and Convergence Laws for Graphs Embeddable on a Fixed Surface ABSTRACT: Let G be a class of labeled graphs with the uniform probability distribution on graphs with a fixed number of vertices. Given a graph property A, we are interested in the limiting probability that A holds in G. It was shown by Heinig et al. that this limiting probability always exists when G is the class of planar graphs and A is any property expressible in monadic second order logic (MSO), and it was conjectured that the same result holds for the class of graphs embeddable on a fixed surface S. After reviewing the results for planar graphs, and more generally for minor-closed classes of graphs, we will refute the conjecture by showing that for every closed surface (orientable or not) other than the sphere there exists an MSO graph property whose limiting probability does not exist. In addition we show that every rational number in [0,1] is the limiting probability of some MSO property, as opposed to the class of planar graphs where there are so-called gaps. The proof relies on a combination of methods from structural graph theory, concretely large face-width embeddings of graphs on surfaces, analytic combinatorics, and finite model theory. This is joint work with Albert Atserias and Stephan Kreutzer. TUESDAY, April 20, 2021 Mathematical logic seminar: 3:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA TUESDAY, April 20, 2021 Set Theory Reading Group: 4:30 P.M., Online, Sandra Müller, University of Vienna Join Zoom Meeting: https://cmu.zoom.us/j/621951121 [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: TBA

Tomorrow: Corey Switzer at 1 30 pm (Toronto Time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Corey Switzer, The Graduate Center, CUNY
Date and Time: Friday, January 29, 2021 - 1:30pm to 3:00pm (Toronto time)
Title: Higher Dimensional Cardinal Characteristics for Sets of Real Valued Functions
Abstract: 

Cardinal characteristics on the generalized Baire and Cantor spaces $\kappa^\kappa$ and $2^\kappa$ have recently generated significant interest. In this talk I will introduce a different generalization of cardinal characteristics, namely to the space of functions $f:\omega^\omega \to \omega^\omega$. Given an ideal $I$ on Baire space and a relation $R$ let us define $f R_I g$ for $f$ and $g$ functions from $\omega^\omega$ to $\omega^\omega$ if and only if $f(x) R g(x)$ for an $I$-measure one set of $x \in \omega^\omega$. By letting $I$ vary over the null ideal, the meager ideal and the bounded ideal; and $R$ vary over the relations $\leq^*$, $\neq^*$ and $\in^*$ we get 18 new cardinal characteristics by considering the bounding and dominating numbers for these relations. These new cardinals form a diagram of provable implications similar to the Cichoń diagram. They also interact in several surprising ways with the cardinal characteristics on $\omega$. For instance, they can be arbitrarily large in models of CH, yet they can be $\aleph_1$ in models where the continuum is arbitrarily large. They are bigger in the Sacks model than the Cohen model. I will introduce these cardinals, show some of the provable implications and discuss what is known about consistent inequalities, focusing on the $\mathfrak{b}$-numbers in well-known models such as the Cohen and Random  model. This is joint work with Jörg Brendle.


Bio: Corey Bacal Switzer is currently a postdoctoral researcher at the Kurt Gödel Research Center For Mathematical Logic in the Mathematics Department of the University of Vienna working under Vera Fischer. He finished his PhD at the CUNY Graduate Center in New York in 2020. His research is in set theory, focusing on forcing, cardinal characteristics and infinite combinatorics

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Logic Seminar 3 Feb 2021 17:00 hrs at NUS by Wong Tin Lok

NUS Logic Seminar
Invitation to the Logic Seminar at the National University of Singapore Date: Wednesday, 3 February 2021, 17:00 hrs Talk via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? Speaker: Wong Tin Lok Title: Arithmetic under negated induction URL: http://www.comp.nus.edu.sg/~fstephan/logicseminar.html Abstract: Arithmetic generally does not admit any non-trivial quantifier elimination. I will talk about one exception, where the negation of an induction axiom is included in the theory. Here the Weak Koenig's Lemma from reverse mathematics arises as a model completion. This work is joint with Marta Fiori-Carones, Leszek Aleksander Kolodziejczyk and Keita Yokoyama.

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER: Richard Matthews (Univ. of Leeds)
TITLE: Taking Reinhardt’s Power Away
TIME: January 27 at 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.








Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609












Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











(KGRC) research seminar talk on Thursday, January 28

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, January 28 "Distributivity spectrum of forcing notions" Marlene Koelbing (KGRC), Wolfgang Wohofsky (KGRC) In our talk, we will introduce two different notions of a spectrum of distributivity of forcings. The first one is the fresh function spectrum, which is the set of regular cardinals lambda, such that the forcing adds a new function with domain lambda all whose initial segments are in the ground model. We will provide several examples as well as general facts how to compute the fresh function spectrum, also discussing what sets are realizable as a fresh function spectrum of a forcing. The second notion is the combinatorial distributivity spectrum, which is the set of possible regular heights of refining systems of maximal antichains without common refinement. We discuss the relation between the fresh function spectrum and the combinatorial distributivity spectrum. We consider the special case of P(omega)/fin (for which h is the minimum of the spectrum), and use a forcing construction to show that it is consistent that the combinatorial distributivity spectrum of P(omega)/fin contains more than one element. This is joint work with Vera Fischer. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

This Friday Talk: Corey Switzer (usual time)

Toronto Set Theory Seminar
Hello everyone,

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speaker information:

Speaker: Corey Switzer, The Graduate Center, CUNY
Date and Time: Friday, January 29, 2021 - 1:30pm to 3:00pm
Title: Higher Dimensional Cardinal Characteristics for Sets of Real Valued Functions
Abstract: 

Cardinal characteristics on the generalized Baire and Cantor spaces $\kappa^\kappa$ and $2^\kappa$ have recently generated significant interest. In this talk I will introduce a different generalization of cardinal characteristics, namely to the space of functions $f:\omega^\omega \to \omega^\omega$. Given an ideal $I$ on Baire space and a relation $R$ let us define $f R_I g$ for $f$ and $g$ functions from $\omega^\omega$ to $\omega^\omega$ if and only if $f(x) R g(x)$ for an $I$-measure one set of $x \in \omega^\omega$. By letting $I$ vary over the null ideal, the meager ideal and the bounded ideal; and $R$ vary over the relations $\leq^*$, $\neq^*$ and $\in^*$ we get 18 new cardinal characteristics by considering the bounding and dominating numbers for these relations. These new cardinals form a diagram of provable implications similar to the Cichoń diagram. They also interact in several surprising ways with the cardinal characteristics on $\omega$. For instance, they can be arbitrarily large in models of CH, yet they can be $\aleph_1$ in models where the continuum is arbitrarily large. They are bigger in the Sacks model than the Cohen model. I will introduce these cardinals, show some of the provable implications and discuss what is known about consistent inequalities, focusing on the $\mathfrak{b}$-numbers in well-known models such as the Cohen and Random  model. This is joint work with Jörg Brendle.


Bio: Corey Bacal Switzer is currently a postdoctoral researcher at the Kurt Gödel Research Center For Mathematical Logic in the Mathematics Department of the University of Vienna working under Vera Fischer. He finished his PhD at the CUNY Graduate Center in New York in 2020. His research is in set theory, focusing on forcing, cardinal characteristics and infinite combinatorics


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

This Week in Logic at CUNY

This Week in Logic at CUNY
This Week in Logic at CUNY:

- - - - Monday, Jan 25, 2021 - - - -



- - - - Tuesday, Jan 26, 2021 - - - -



- - - - Wednesday, Jan 27, 2021 - - - -



- - - - Thursday, Jan 28, 2021 - - - -



- - - - Friday, Jan 29, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Jan 29, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

Erin Carmody, Fordham University
The relationships between measurable and strongly compact cardinals: Part II

This talk is about the ongoing investigation of the relationships between measurable and strongly compact cardinals. I will present some of the history of the theorems in this theme, including Magidor's identity crisis, and give new results. The theorems presented are in particular about the relationships between strongly compact cardinals and measurable cardinals of different Mitchell orders. One of the main theorems is that there is a universe where κ1κ1 and κ2κ2 are the first and second strongly compact cardinals, respectively, and where κ1κ1 is least with Mitchell order 1, and κ2κ2 is the least with Mitchell order 2. Another main theorem is that there is a universe where κ1κ1 and κ2κ2 are the first and second strongly compact cardinals, respectively, with κ1κ1 the least measurable cardinal such that o(κ1)=2o(κ1)=2 and κ2κ2 the least measurable cardinal above κ1κ1. This is a joint work in progress with Victoria Gitman and Arthur Apter.




Next Week in Logic at CUNY:

- - - - Monday, Feb 1, 2021 - - - -



- - - - Tuesday, Feb 2, 2021 - - - -

Models of Peano Arithmetic (MOPA)
Wednesday, Dec 9, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.

James Walsh, Cornell University
Reducing omega-model reflection to iterated syntactic reflection

Two types of principles are commonly called “reflection principles” in reverse mathematics. According to syntactic reflection principles for T, every theorem of T (from some complexity class) is true. According to semantic reflection principles, every set belongs to some (sufficiently correct) model of T. We will present a connection between syntactic reflection and semantic reflection in second-order arithmetic: for any Pi^1_2 axiomatized theory T, every set is contained in an omega model of T if and only if every iteration of Pi^1_1 reflection for T along a well-ordering is Pi^1_1 sound. There is a thorough proof-theoretic understanding of the latter in terms of ordinal analysis. Accordingly, these reductions yield proof-theoretic analyses of omega-model reflection principles. This is joint work with Fedor Pakhomov.



- - - - Wednesday, Feb 3, 2021 - - - -



- - - - Thursday, Feb 4, 2021 - - - -



- - - - Friday, Feb 5, 2021 - - - -

Set Theory Seminar
CUNY Graduate Center
Friday, Feb 5, 2pm
The seminar will take place virtually at 2pm US Eastern Standard Time. Please email Victoria Gitman (vgitman@nylogic.org) for meeting id.
Andreas Blass, University of Michigan
TBA


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Two talks by B. Siskind on February 9

Carnegie Mellon Logic Seminar
TUESDAY, February 9, 2021 Mathematical logic seminar:  3:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Order-preserving Martin’s Conjecture ABSTRACT: Martin’s Conjecture is a precise way of asserting that, up to equivalence, the only natural functions on the Turing degrees are the familiar ones: the constant functions, the identity, the Turing jump, and the transfinite iterates of the Turing jump. This conjecture is open even restricted to low-level Borel functions, but there have been partial results over the years which show it holds for classes of functions meeting requirements orthogonal to definability. Our recent result is that part of Martin’s Conjecture (lately called “part one”) holds for the class of order-preserving functions. In particular, it follows that the full Martin’s Conjecture holds for Borel order-preserving functions. We’ll talk about Martin’s Conjecture broadly and say something about this recent work. This is joint work with Patrick Lutz. TUESDAY, February 9, 2021 Set Theory Reading Group:  4:30 P.M., Online, Benjamin Siskind, University of California, Berkeley Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Measure-preserving functions on the Turing degrees ABSTRACT: One proof of part one of Martin’s Conjecture for order-preserving functions works for a bigger class of functions: those which are measure-preserving for the Martin measure, in the sense of ergodic theory. Looking at this class of functions brings out more set-theoretic aspects of Martin’s Conjecture. For example, part one of Martin’s Conjecture is equivalent to the non-existence of other non-principal ultrafilters on the Turing degrees Rudin-Keisler below the Martin measure. We’ll talk about the proof of part one of Martin’s Conjecture for this class of functions and some consequences. This is joint work with Patrick Lutz.

Tomorrow two talks (11 am and 1 30 pm)

Toronto Set Theory Seminar
Hello everyone,

To start the semester we will have two talks: one at 11 am (Toronto time) and another at 1 30 pm (Toronto time).

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speakers information:

Speaker:Dima Sinapova, UIC, University of Illinois at Chicago, University of Illinois, Chicago
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Title: Iteration, reflection, and singular cardinals
Abstract:

Two classical results of Magidor are: (1) from large cardinals it is consistent to have reflection at  $\aleph_{\omega+1}$ and (2) from large cardinals it is consistent to have the failure of SCH at $\aleph_{\omega}$.

These principles are at odds with each other. The former is a compactness type principle. (Compactness is the phenomenon where if a certain property holds for every smaller substructure of an object, then it holds for the entire object.) In contrast, failure of SCH is an instance of incompactness. The natural question is whether we can have both of these simultaneously. We show the answer is yes.

We describe a Prikry style iteration, and use it to force stationary reflection in the presence of not SCH. Then we obtain this situation at  $\aleph_{\omega}$ . This is joint work with Alejandro Poveda and Assaf Rinot.


Speaker: Marcos Mazari Armida, Carnagie Mellon University
Date and Time: Friday, January 22, 2021 - 1:30pm to 3pm
Title: Universal models in classes of abelian groups and modules
Abstract:

The search for universal models began in the early  twentieth century when Hausdorff showed that there is a  universal linear order of cardinality $\aleph_{n+1}$ if $2^{\aleph_n}= \aleph_{n + 1}$, i.e., a linear order $U$ of cardinality $\aleph_{n+1}$ such that every linear order of cardinality $\aleph_{n+1}$ embeds in $U$. In this talk, we will study universal models in several classes of abelian groups and modules with respect to  pure embeddings. In particular, we will present a complete solution below $\aleph_\omega$, with the exception of $\aleph_0$ and $\aleph_1$, to Problem 5.1 in page 181 of \emph{Abelian Groups} by L\'{a}szl\'{o} Fuchs, which asks to find the cardinals $\lambda$ such that there is a universal abelian p-group for purity of cardinality $\lambda$. The solution presented will use both model-theoretic and set-theoretic ideas.

Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Two events on February 16

Carnegie Mellon Logic Seminar
TUESDAY, February 16, 2021 Mathematical logic seminar:  3:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: The definable content of (co)homological invariants: Cech cohomology ABSTRACT: In this talk we will develop a framework for enriching various classical invariants of homological algebra and algebraic topology with additional descriptive set-theoretic information. The resulting "definable invariants" can be used for much finer classification than their purely algebraic counterparts. We will then illustrate how these ideas apply to the classical Cech cohomology theory, by introducing a new invariant for locally compact metrizable spaces up to homotopy equivalence which we call "definable cohomology". In strong contrast to its classical counterpart, this definable cohomology theory provides complete classification to homotopy classes of mapping telescopes of d-tori, and for homotopy classes of maps from mapping telescopes of d-tori to spheres. The latter problem was raised in the d=1 case by Borsuk and Eilenberg in 1936. This is joint work with Jeffrey Bergfalk and Martino Lupini. TUESDAY, February 16, 2021 Set Theory Reading Group:  4:30 P.M., Online, Aristotelis Panagiotopoulos, University of Muenster Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ulam stability for quotients of abelian non-archimedean Polish groups ABSTRACT: Based on an earlier work of Shelah concerning the relationship of the continuum hypothesis to the cardinality of the set of automorphisms of $\mathcal{P}(\omega)/\mathrm{fin}$, Velickovic showed that if such an automorphism admits a Borel lift $\mathcal{P}(\omega)\to \mathcal{P}(\omega)$, then it is of a certain "trivial" form. Similarly, Kanovei and Reeken showed that if $N,M$ are countable dense subgroups of $\mathbb{R}$, then every homomorphism $\mathbb{R}/N\to \mathbb{R}/M$ with a Borel lift $\mathbb{R}\to \mathbb{R}$, is of a certain "trivial" form. Kanovei and Reeken asked whether quotients of the $p$-adic groups satisfy similar "Ulam stability" phenomena. In this talk, we will settle this question by providing Ulam-stability phenomena for definable homomorphisms $G/N\to H/M$ when $G,H$ are arbitrary abelian non-archimedean Polish groups and $N,M$ are Polishable subgroups. We will then illustrate how such rigidity results are in the heart of the definable cohomology theory which we developed in the previous talk. This is joint work with Jeffrey Bergfalk and Martino Lupini.

On Logic Seminar This Semester

NUS Logic Seminar
Dear Attendees of the logic seminar, I would like to ask for volunteers who can give talks over Zoom at 17:00 hrs Singapore time, see http://www.comp.nus.edu.sg/~fstephan/logicseminar.html for free time-slots (currently all and I will put the names of those who reserve a slot into their preferred time-slot). Furthermore, for tomorrow, you might consider attending the talk of Brian Rabern from the University of Edinburgh at FASS on quantification as modelled by Frege and by Taski and the philosophical discussion will be moderated by Ben Blumson, NUS. Best regards, Frank `

(KGRC) research seminar talk on Thursday, January 21

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, January 21 "Strong colourings over partitions" Juris Steprāns (York University, Toronto, Canada) The celebrated result of Todorcevic that $\aleph_1\not\rightarrow [\aleph_1]^2_{\aleph_1}$ provides a well known example of a strong colouring. A mapping $c:[\omega_1]^2\to \kappa$ is a strong colouring over a partition $p:[\omega_1]^2\to \omega$ if for every uncountable $X\subseteq \omega_1$ there is $n\in \omega$ such that the range of $c$ on $[X]^2\cap p^{-1}\{n\}$ is all of $\kappa$. I will discuss some recent work with A. Rinot and M. Kojman on negative results concerning strong colourings over partitions and their relation to classical results in this area. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER: Vera Fisher (Wien)
TITLE:  Independent families in the countable and the uncountable
TIME: January 20 at 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.




Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











BLAST 2021: June 9-13

Conference
BLAST 2021 June 9-13, 2021 New Mexico State University, Las Cruces, NM, USA ONLINE Conference website: https://math.nmsu.edu/blast-2021/ Conference email: blast@nmsu.edu Submission link: https://easychair.org/conferences/?conf=blast2021 SCOPE BLAST is a conference series focusing on Boolean Algebras, Lattices, Algebraic Logic, Universal Algebra, Set Theory, Set-theoretic Topology, and Point-free Topology. The series circulates between different universities. The central BLAST web page, with links to past meetings, can be found here: http://math.colorado.edu/blast/ This year's installment of BLAST will take place at New Mexico State University. The scientific program will include invited lectures, tutorial lectures, two special sessions, and contributed talks. Due to the current pandemic, the conference will be entirely online. INVITED SPEAKERS: Aichinger, Erhard (Johannes Kepler University Linz) Carai, Luca (New Mexico State University) Celani, Sergio (National University of the Center of the Buenos Aires Province) Fisher, Vera (University of Vienna) Gehrke, Mai (University of Cote d’Azur, Nice) Hrusak, Michael (National Autonomous University of Mexico) Lapenta, Serafina (University of Salerno) Zamojska-Dzienio, Anna (Warsaw University of Technology) TUTORIALS: Bodirsky, Manuel (Dresden University of Technology) Dow, Alan (UNC Charlotte) Jung, Achim (University of Birmingham) SPECIAL SESSIONS: SPECIAL SESSION IN MEMORY OF W. CHARLES HOLLAND (1935—2020) AND JORGE MARTINEZ (1945—2020) Organizers: Rick Ball (University of Denver) and Warren McGovern (Florida Atlantic University) Speakers: Ball, Rick (University of Denver) Darnel, Michael (Indiana University South Bend) Droste, Manfred (University of Leipzig) Dube, Themba (University of South Africa) Dvurečenskij, Anatolij (Mathematical Institute, Slovak Academy of Sciences) Hager, Anthony (Wesleyan University) Marra, Vincenzo (University of Milan) McGovern, Warren (Florida Atlantic University) Schwartz, Niels (University of Passau) Tsinakis, Constantine (Vanderbilt University) SPECIAL SESSION ON STONE AND PRIESTLEY DUALITIES Speakers: Borlido, Célia (University of Coimbra) van Gool, Sam (University of Paris) Holliday, Wesley (UC Berkeley) Jibladze, Mamuka (Razmadze Mathematical Institute, Tbilisi State University) Melliès, Paul-André (University of Paris) Reggio, Luca (University of Oxford) Salvati, Sylvain (University of Lille) Tressl, Marcus (University of Manchester) CONTRIBUTED TALKS: Abstracts of contributed talks should be submitted through EasyChair: https://easychair.org/conferences/?conf=blast2021 Please indicate if you would like to submit to a special session. The abstract should not exceed 2 pages. IMPORTANT DATES: 11 April, 2021: Deadline for submitting abstracts of contributed talks 25 April, 2021: Notification of acceptance 9 June, 2021: Start of the conference 13 June, 2021: End of the conference LOCAL ORGANIZING COMMITTEE: Albee, Kempton (grad student) Bezhanishvili, Guram Carai, Luca (grad student) Harding, John Morandi, Pat Olberding, Bruce Peinado, Miguel (grad student) Raviprakash, Ranjitha (grad student) Shapirovsky, Ilya Sinclaire, Morgan (grad student)
Link to more info

Two events on February 2

Carnegie Mellon Logic Seminar
TUESDAY, February 2, 2021 Mathematical logic seminar:  3:30 P.M., Online, Anush Tserunyan, McGill University Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ergodic theorems along trees ABSTRACT: In the classical pointwise ergodic theorem for a probability measure preserving (pmp) transformation $T$, one takes averages of a given integrable function over the intervals $\{x, T(x), T^2(x), \hdots, T^n(x)\}$ in front of the point $x$. We prove a “backward” ergodic theorem for a countable-to-one pmp $T$, where the averages are taken over subtrees of the graph of T that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). Surprisingly, this theorem yields forward ergodic theorems for countable groups, in particular, one for pmp actions of free groups of finite rank, where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. This strengthens Bufetov’s theorem from 2000, which was the most general result in this vein. This is joint work with Jenna Zomback. TUESDAY, February 2, 2021 Set Theory Reading Group:  4:30 P.M., Online, Jenna Zomback, University of Illinois at Urbana-Champaign Join Zoom Meeting: https://cmu.zoom.us/j/621951121  [cmu.zoom.us] Meeting ID: 621 951 121 TITLE: Ergodic theorems along trees: the proofs ABSTRACT: In this continuation of the previous talk, we discuss a backward (inverse) ergodic theorem for a probability measure preserving (pmp) transformation $T$, where the averages are taken over subtrees of the graph of $T$ that are rooted at $x$ and lie behind $x$ (in the direction of $T^{-1}$). We will derive from it a new (forward) pointwise ergodic theorem for pmp actions of free groups of finite rank, where the averages are taken along subtrees of the standard Cayley graph rooted at the identity. We will then discuss a very short proof (due to Tserunyan) of the classical pointwise ergodic theorem, and, using this proof as an outline, we will sketch the proof of the backward ergodic theorem. This is joint work with Anush Tserunyan.

Two talks next week (January 22nd)

Toronto Set Theory Seminar
There was a Typo in the last email. Here the correction:

Speaker:Dima Sinapova, UIC, University of Illinois at Chicago, University of Illinois, Chicago
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Location: Online
Abstract: (In previous email)

Speaker: Marcos Mazari Armida, Carnagie Mellon University
Date and Time: Friday, January 22, 2021 - 1:30pm to 3pm
Title: Universal models in classes of abelian groups and modules
Abstract: (In previous email)


Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com


On Fri, Jan 15, 2021 at 5:19 PM Ivan Ongay Valverde <ivan.ongay.valverde@gmail.com> wrote:
Hello everyone,

To start the semester we will have two talks: one at 11 am (Toronto time) and another at 1 30 pm (Toronto time).

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speakers information:

Speaker:Dima Sinapova, UIC, University of Illinois at Chicago, University of Illinois, Chicago
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Location: Online
Abstract:

Two classical results of Magidor are: (1) from large cardinals it is consistent to have reflection at  $\aleph_{\omega+1}$ and (2) from large cardinals it is consistent to have the failure of SCH at $\aleph_{\omega}$.

These principles are at odds with each other. The former is a compactness type principle. (Compactness is the phenomenon where if a certain property holds for every smaller substructure of an object, then it holds for the entire object.) In contrast, failure of SCH is an instance of incompactness. The natural question is whether we can have both of these simultaneously. We show the answer is yes.

We describe a Prikry style iteration, and use it to force stationary reflection in the presence of not SCH. Then we obtain this situation at  $\aleph_{\omega}$ . This is joint work with Alejandro Poveda and Assaf Rinot.


Speaker: Marcos Mazari Armida, Carnagie Mellon University
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Title: Universal models in classes of abelian groups and modules
Abstract:

The search for universal models began in the early  twentieth century when Hausdorff showed that there is a  universal linear order of cardinality $\aleph_{n+1}$ if $2^{\aleph_n}= \aleph_{n + 1}$, i.e., a linear order $U$ of cardinality $\aleph_{n+1}$ such that every linear order of cardinality $\aleph_{n+1}$ embeds in $U$. In this talk, we will study universal models in several classes of abelian groups and modules with respect to  pure embeddings. In particular, we will present a complete solution below $\aleph_\omega$, with the exception of $\aleph_0$ and $\aleph_1$, to Problem 5.1 in page 181 of \emph{Abelian Groups} by L\'{a}szl\'{o} Fuchs, which asks to find the cardinals $\lambda$ such that there is a universal abelian p-group for purity of cardinality $\lambda$. The solution presented will use both model-theoretic and set-theoretic ideas.



Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

Two talks next week (January 22nd)

Toronto Set Theory Seminar
Hello everyone,

To start the semester we will have two talks: one at 11 am (Toronto time) and another at 1 30 pm (Toronto time).

Please use the following link and fill the form (every week) to enter the meeting. This form helps the Field Institute to know statistical data about attendance.


Here the speakers information:

Speaker:Dima Sinapova, UIC, University of Illinois at Chicago, University of Illinois, Chicago
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Location: Online
Abstract:

Two classical results of Magidor are: (1) from large cardinals it is consistent to have reflection at  $\aleph_{\omega+1}$ and (2) from large cardinals it is consistent to have the failure of SCH at $\aleph_{\omega}$.

These principles are at odds with each other. The former is a compactness type principle. (Compactness is the phenomenon where if a certain property holds for every smaller substructure of an object, then it holds for the entire object.) In contrast, failure of SCH is an instance of incompactness. The natural question is whether we can have both of these simultaneously. We show the answer is yes.

We describe a Prikry style iteration, and use it to force stationary reflection in the presence of not SCH. Then we obtain this situation at  $\aleph_{\omega}$ . This is joint work with Alejandro Poveda and Assaf Rinot.


Speaker: Marcos Mazari Armida, Carnagie Mellon University
Date and Time: Friday, January 22, 2021 - 11am to 12:30pm
Title: Universal models in classes of abelian groups and modules
Abstract:

The search for universal models began in the early  twentieth century when Hausdorff showed that there is a  universal linear order of cardinality $\aleph_{n+1}$ if $2^{\aleph_n}= \aleph_{n + 1}$, i.e., a linear order $U$ of cardinality $\aleph_{n+1}$ such that every linear order of cardinality $\aleph_{n+1}$ embeds in $U$. In this talk, we will study universal models in several classes of abelian groups and modules with respect to  pure embeddings. In particular, we will present a complete solution below $\aleph_\omega$, with the exception of $\aleph_0$ and $\aleph_1$, to Problem 5.1 in page 181 of \emph{Abelian Groups} by L\'{a}szl\'{o} Fuchs, which asks to find the cardinals $\lambda$ such that there is a universal abelian p-group for purity of cardinality $\lambda$. The solution presented will use both model-theoretic and set-theoretic ideas.



Iván Ongay Valverde (he/his)

My email account ongay@math.wisc.edu will be closed in October 2020. Please contact me either at ongay@yorku.ca or at ivan.ongay.valverde@gmail.com

(KGRC) research seminar talk on Thursday, January 14

Kurt Godel Research Center
Research seminar Kurt Gödel Research Center Thursday, January 14 "Infinitary combinatorics and strong homology" Jeffrey Bergfalk (KGRC) Motivated by several recent advances, we will provide a research history of the main set-theoretic problems arising in the study of strong homology. As such, this talk will overlap with one on the same theme given in Paris-Lyon Logic Seminar last fall. We will presume no awareness in our audience either of strong homology or of that talk, but will aim in this one to provide, along with the necessary background, some sketch of the main ideas behind several recent arguments. This is an area in which simplicial principles and infinitary combinatorics come together. Its questions, at heart, have tended to be questions about higher-dimensional variants of classical set-theoretic concerns (like nontrivial coherence, $\Delta$ systems, etc.); these questions, in turn, increasingly appear to be of some interest in their own right. Time and Place Talk at 3:00pm via Zoom: This talk will be given via Zoom. If you have not received the meeting link by the day before the talk, please contact richard.springer@univie.ac.at!

Barcelona Set theory Seminar

Barcelona Logic Seminar
Dear All, 

Please find attached the announcement of the next session of the Barcelona Set Theory Seminar. Feel free to distribute it. 

SPEAKER: Trevor M. Wilson (Miami Univ.)
TITLE: The large cardinal strength of Vopenka's Principle for trees and for rayless trees
TIME: January 13 at 16:00 (CET)
PLACE: The Seminar will take place online at the following address:


Best regards,
Joan

P.S.: If you do not wish to receive any more announcements, please send an email to bagaria@ub.edu with the text “Unsubscribe”.







Joan Bagaria 
ICREA Research Professor 
Universitat de Barcelona
Departament de Matemàtiques i Informàtica
Gran Via de les Corts Catalanes 585
08007 Barcelona
Catalonia 

Phone: +34 93 402 1609











Logic Seminar at NUS on Wednesday 13 Jan 2021 17:00 hrs - World Logic Day Special

NUS Logic Seminar
Dear colleagues, This week's Logic Seminar on Wed 13 January 2021 at 17:00 hrs is an open session where, in light of the World Logic Day on Thursday, everyone is encouraged to give a 5 to 10 minutes presentation about his favourate result or results of his own work. In the case that you have no slides for this, feel free to share a Word file and type into it on Zoom. The result can be from any time where you have been working on logic, it should give the statement and contribution of the theorem. If you want to give a longer talk, we will schedule one in the next weeks. Best regards, Frank Here again the details: Wednesday 13 Jan 2021 17:00 hrs Singapore Time (+800) World Logic Seminar Special - Share your nicest results Discussion via Zoom: https://nus-sg.zoom.us/j/96860201432?pwd=cVdwZmd2clVFaEhaTmJjaGdXMFdmdz09 Meeting ID: 968 6020 1432 Password: Is P=NP? You might reply with a short email to Frank Stephan (fstephan@comp.nus.edu.sg) and Yang Yue (matyangy@nus.edu.sg) if you follow our request for a short talk of 5 to 10 minutes, just for planning purposes. Best regards, Frank